Balbharti Maharashtra State Board Class 9 Science Solutions Chapter 5 Acids, Bases and Salts Notes, Textbook Exercise Important Questions and Answers.
Class 9 Science Chapter 5 Acids, Bases and Salts Textbook Questions and Answers
1. Identify the odd one out and justify.
(a) Chloride, nitrate, hydride, ammonium
Answer:
Ammonium is the odd one out as it is a basic radical and rest all are acidic radicals. Generally, basic radicals are formed by the removal of electrons from the atom of metals such as Na+, Cu2+. But there are some exceptions, such as NH4+.
(b) Hydrogen chloride, sodium hydroxide, calcium oxide, ammonia
Answer:
Hydrogen chloride is the odd one out. It is acidic and rest all are basic.
(c) Acetic acid, carbonic acid, hydrochloric acid, nitric acid
Answer:
Carbonic acid is the odd one out. It is a dibasic acid and rest are all monobasic acids.
(d) Ammonium chloride, sodium chloride, potassium nitrate, sodium sulphate
Answer:
Ammonium chloride is the odd one out, as it is made up of a strong acid and weak base and rest all are formed from strong acid and strong base.
(e) Sodium nitrate, sodium carbonate, sodium sulphate, sodium chloride
Answer:
Sodium carbonate is the odd one out, as it is made up of a weak acid and strong base, and rest all are formed from strong acid and strong base.
(f) Calcium oxide, magnesium oxide, zinc oxide, sodium oxide.
Answer:
Zinc oxide is the odd one out, as it is an amphoteric oxide, and rest all are basic oxides.
(g) Crystalline blue vitriol, crystalline common salt, crystalline ferrous sulphate, crystalline sodium carbonate.
Answer:
Crystalline common salt is the odd one out, as it does not contain water of crystallisation. It is an ionic compound and ionic compounds are crystalline in nature and rest all have their crystalline structure because of their water of crystallization.
(h) Sodium chloride, potassium hydroxide, acetic acid, sodium acetate.
Answer:
Acetic acid is the odd one out. It is an acid, the rest are all salts.
2. Write down the changes that will be seen in each instance and explain the reason behind it.
(a) 50ml water is added to 50ml solution of copper sulphate.
Answer:
(b) Two drops of the indicator phenolphthalein were added to 10ml solution of sodium hydroxide.
Answer:
(c) Two or three filings of copper were added to 10ml dilute nitric acid and stirred.
Answer:
When copper metal reacts with dilute nitric acid, the metal does not displace hydrogen from the acid like reaction with other metals. Instead the reaction produces nitric oxide, (NO).
(d) A litmus paper was dropped into 2ml dilute HCl. Then 2ml concentrated NaOH was added to it and stirred.
Answer:
Blue litmus Paper:
Red litmus paper:
(e) Magnesium oxide was added to dilute HCl and magnesium oxide was a added to dilute NaOH.
Answer:
(i) Magnesium oxide + dil HCl.
This is a neutralization reaction. Magnesium oxide is an insoluble base, it reacts with dilute HCl to produce a soluble salt MgCl2 and water H2O.
\(\mathrm{MgO}_{(\mathrm{s})}+2 \mathrm{HCl}_{(\mathrm{aq})} \longrightarrow \mathrm{MgCl}_{2(\mathrm{aq})}+\mathrm{H}_{2} \mathrm{O}_{(n)}\)
(ii) Magnesium oxide + NaOH.
No chemical reaction takes place between magnesium oxide and sodium hydroxide.
(f) Zinc oxide was added to dilute HCl and zinc oxide was added to dilute NaOH.
Answer:
(g) Dilute HCl was added to limestone.
Answer:
(h) Pieces of blue vitriol were heated in a test tube. On cooling, water was added to it.
Answer:
(i) Dilute H2SO4 was taken in an electrolytic cell and electric current was passed through it.
Answer:
[H+ ions gains electrons and are converted to hydrogen gas]
\(2 \mathrm{H}^{+}+2 \mathrm{e}^{-} \longrightarrow \mathrm{H}_{2(\mathrm{~g})}\)
Cathode reaction:
\(2 \mathrm{H}_{2} \mathrm{O}_{(\mathrm{i})}+2 \mathrm{e}^{-} \longrightarrow \mathrm{H}_{2(\mathrm{~g})}+2 \mathrm{OH}_{(\mathrm{aq})}^{-}\)
Anode reaction:
\(2 \mathrm{H}_{2} \mathrm{O}_{(\mathrm{l})} \longrightarrow \mathrm{O}_{2(\mathrm{~g})}+4 \mathrm{H}_{(\mathrm{aq})}^{+}+4 \mathrm{e}\)
3. Classify the following oxides into three types and name the types.
CaO, MgO, CO2, SO3, Na2O, ZnO, Al2O3, Fe2O3
Answer:
There are three types of oxides : Basic oxides, Acidic oxides and Amphoteric oxides.
| Basic oxides | Acidic oxides | Amphoteric oxides |
| CaO | CO2 | ZnO |
| MgO | SO3 | Al2O3 |
| Na2O | ||
| Fe2O3 |
Generally metal oxides are basic in nature.
Exception : Al2O3 and ZnO are amphoteric oxides.
Generally non-metal oxides are acidic in nature.
4. Explain by drawing a figure of the electronic configuration.
a. Formation of sodium chloride from sodium and chlorine.
Answer:
b. Formation of a magnesium chloride from magnesium and chlorine.
Answer:
5. Show the dissociation of the following compounds on dissolving in water, with the help of chemical equation and write whether the proportion of dissociation is small or large.
Hydrochloric acid, Sodium chloride, Potassium hydroxide, Ammonia, Acetic acid, Magnesium chloride, Copper sulphate.
Answer:
(a) Hydrochloric acid (HCl)
(b) Sodium chloride (NaC1)
(c) Potassium hydroxide (KOH)
(d) Ammonia (NH3)
(i) \(\mathrm{NH}_{3(\mathrm{~g})}+\mathrm{H}_{2} \mathrm{O}_{(\mathrm{n}}-\frac{\text { Water }}{\text { uissociation }}>\mathrm{NH}_{4 \text { (aq) }}^{+}+\mathrm{OH}_{\text {(aq) }}^{-}\)
(ii) Ammonia dissolves in water to form NH4OH (ammonium hydroxide). NH4OH does not dissociate completely as it is a weak base. The aqueous solution contains a small proportion of OH– ions and the concerned basic radical along with a large proportion of undissociated molecules of the base i.e. NH4OH.
(iii) The proportion of dissociation is small.
(e) Acetic acid (CH3COOH)
(f) Magnesium chloride (MgCl2)
(g) Copper sulphate (CuSO4)
6. Write down the concentration of each of the following solutions in g/L and mol/L.
a. 7.3g HCl in 100ml solution
b. 2g NaOH in 50ml solution
c. 3g CH3COOH in 100ml solution
d. 4.9g H2SO4 in 200ml solution
Answer:
To find : The concentration in g/L.
Solution:
7. Obtain a sample of rainwater. Add to it a few drops of universal indicator. Meausre its pH. Describe the nature of the sample of rainwater and explain the effect if it has on the living world.
Answer:
8. Answer the following questions.
a. Classify the acids according to their basicity and give one example of each type.
Answer:
b. What is meant by neutralization? Give two examples from everyday life of the neutralization reaction.
Answer:
Examples in daily life:
c. Explain what is meant by electrolysis of water. Write the electrode reactions and explain them.
Answer:
Electrolysis of water:
9. Give a reason for the following.
a. Hydronium ions are always in the form H3O+.
Answer:
b. Buttermilk spoils if kept in a copper or brass container.
Answer:
10. Write the chemical equations for the following activities.
(a) NaOH solution was added to HCl solution.
Answer:
When NaOH reacts with HCl, it gives NaCl and water.
(b) Zinc dust was added to dilute H2SO4.
Answer:
When zinc reacts with dilute sulphuric acid, it forms zinc sulphate and hydrogen gas is liberted.
(c) Dilute nitric acid was added to calcium oxide.
Answer:
When dilute nitric acid reacts with calcium oxide, it forms calcium nitrate and water.
(e) Carbon dioxide gas was passed through KOH solution.
(f) Dilute HCl was poured on baking soda.
11. State the differences.
a. Acids and bases
Answer:
| Acids | Bases |
| (i) A substance which liberates H+ ions when dissolved in water is an acid (ii) Blue litmus turns red in an acid. (iii) The pH of an acid is less than 7. (iv) Acids are sour to taste (v) e.g. HCl, H2SO4 |
A substance which liberates OH– ions when dissolved in water is called a base. Red litmus turns blue in a base The pH of a base is greater than 7. Bases are bitter to taste, e.g. NaOH, KOH. |
b. Cation and anion
Answer:
| Cations | Anions |
| (i) Cations are ions with a net positive charge. | Anions are ions with a net negative charge. |
| (ii) Cations are generally formed by metals. When metals donate electrons, they have excess of protons, hence they form cations. | Anions are generally formed by non-metals. When non-metals accept electrons, they have excess of electrons, hence they form anions. |
| (iii) Cations are attracted towards the cathode which are negatively charged electrodes. | Anions are attracted towards the anode which are positively charged electrodes. |
| (iv) e.g.: Na+, Ca2+, Mg2+, K+ etc. | e.g.: O2 , S2-, Cl–, Br– etc. |
c. the Negative electrode and the positive electrode.
Answer:
| Negative Electrode | Positive Electrode |
| (i) Negatively charged electrodes are called as a cathode. | Positively charged electrodes are called as Anode. |
| (ii) Positively charged cations move towards the cathode or negative electrode. | Negatively charged anions move towards the anode or positive electrode. |
| (iii) Cathode accepts electrons from cations | Anode gives electrons to anions |
12. Classify aqueous solutions of the following substances according to their pH into three groups : 7, more than 7, less than 7.
Common salt, sodium acetate, hydrochloric acid, carbon dioxide, potassium bromide, calcium hydroxide, ammonium chloride, vinegar, sodium carbonate, ammonia, sulphur dioxide.
Answer:
| pH = 7 | pH > 7 | pH < 7 |
| (a) common salt. | sodium acetate. | sulphur dioxide. |
| (b) potassium bromide. | sodium carbonate | hydrochloric acid. |
| (c) | ammonia. | carbon-dioxide. |
| (d) | calcium hydroxide. | ammonium chloride. |
| (e) | vinegar |
Class 9 Science Chapter 5 Acids, Bases and Salts Intext Questions and Answers
Question 1.
How are the following substances classified into three groups with the help of litmus?
Lemon, tamarind, baking soda, buttermilk, vinegar, orange, milk, lime, tomato, milk of magnesia, water, alum.
Answer:
| Basic Substance: Turns Red Litmus Blue | Acidic Substance: Turns Blue Litmus Red | Neutral Substance: No change in the colour of litmus |
| Baking Soda | Lemon | water |
| Lime | Tamarind | |
| Milk of Magnesia | Buttermilk | |
| Vinegar | ||
| Orange | ||
| Milk | ||
| Tomato | ||
| Alum |
Question 2.
Fill in the columns in the part of the following table:
Answer:
Question 3.
Complete the following table of the concentration of various aqueous solutions.
Answer:
Question 4.
Complete the following table of neutralization reactions and also write down the names of the acids, bases and salts in it.
Answer:
Question 5.
What are the names of the following compounds? NH3, Na2O, CaO.
Answer:
NH3 : Ammonia
Na2O : Sodium oxide
CaO : Calcium oxide
Question 6.
Into which type will you classify the above compounds, acid, base or salt?
Answer:
NH3 : base
Na2O : base
CaO : base
Question 7.
ive examples of monobasic, dibasic and tribasic acids.
Answer:
Monobasic acid examples: HNO3, HCl, CH3COOH
Dibasic acid examples: H2SO4, H2CO3
Tribasic acid examples: H3BO3, H3PO4
Question 8.
Give the three types of bases with their examples.
Answer:
Types of bases:
Monoacidic base examples : NaOH, KOH, NH4OH
Diacidic base examples: Ca(OH)2, Ba(OH)2
Triacidic base examples: A(OH)3, Fe(OH)3
Question 9.
What are the colours of the following natural and synthetic indicators in acidic and basic solutions? Litmus, turmeric, jamun, methyl orange, phenolphthalein?
Answer:
| Indicator | Colour in Acidic Solution | Colour in basic Solution |
| Litmus | Red | Blue |
| Turmeric | Yellow | Red |
| Jamun | Red | Blue-Green |
| Methyl orange | Red | Yellow |
| Phenolphthalein | Colourless | Pink |
Question 10.
On mixing the substances as shown here, what are the resulting mixtures formed by mixing the following substances called?
(a) Water and salt
(b) Water and sugar
(c) Water and sand
(d) Water and sawdust
Answer:
(a) Water and salt – Homogeneous mixture
(b) Water and sugar – Homogeneous mixture
(c) Water and sand – Heterogeneous mixture
(d) Water and sawdust – Heterogeneous mixture
Question 11.
What would be the definition of an acid and a base with reference to the neutralization reaction?
Answer:
Answer the following questions:
Question 1.
Take aqueous solution of sodium chloride, copper sulphate, glucose, urea, dil.H2SO4 and dil.NaOH in a beaker and test the electrical conductivity of the solutions. Answer the given below questions.
(a) With which solutions did the bulb glow?
Answer:
Solutions with which bulb glows: Aqueous solution of NaCl, CuSO4, H2SO4 and NaOH.
(b) Which solutions are electrical conductors?
Answer:
Solutions which are electrical conductors:
NaCl, CuSO4, H2SO4 and NaOH.
Question 2.
During electrolysis of copper sulphate, if electric current is passed through the electrolytic cell for a long time, what change would be seen at the anode?
Answer:
Question 3.
Would water be a good conductor of electricity?
Answer:
Pure water is not a good conductor of electricity.
Answer the following questions:
Question 1.
(i) With which solutions did the bulb glow?
(ii) Which solutions are electrical conductors?
Answer:
(i) The bulbs glows when the wire are immersed in NaCl solution.
(ii)
| Solution | Results | |
| 1g Copper Sulphate Solution | Bulb glow | |
| 1g Glucose Solution | Bulb does not glow | |
| 1g Urea Solution | Bulb does not glow | |
| 5ml dil.H2SO4 Solution | Bulb glows | |
| 5ml dil. NaOH Solution | Bulb glows | |
Question 2.
What would be the definition of an acid and a base with reference to the neutralization reaction?
Answer:
Question 3.
Dissolve 2g salt in 500ml pure water. Take 250 ml of this solution in a 500ml capacity beaker. Connect two electrical wires to the positive and negative terminals of a power supply. Remove the insulating cladding from about 2cm portions at the other ends of the wires. These are the two electrodes. Fill two test tubes upto the brim with the prepared dilute salt solution. Invert them on the electrodes without allowing any air to enter. Start the electric current under 6V potential difference from the power supply. Observe what happens in the test tubes after some time.
(a) Did you see the gas bubbles forming near the electrodes in the test tubes?
(b) Are these gases heavier or lighter than water?
(c) Are the volumes of the gases collected over the solution in the two test tubes the same or different?
(d) Test the solutions in the two test tubes with litmus paper, what do you see?
(e) Repeat the activity by using dilute H2SO4 as well as dilute NaOH as the electrolyte.
Answer:
(a) Yes, gas bubbles can be seen forming near the electrodes in the test tube.
(b) These gases are lighter than water.
(c) The volumes of gases collected over the solution in the two test tubes are different.
(d) The solution in the cathode turns red litmus blue while solution in anode turns blue litmus red.
(e) When the above experiment is repeated with dil H2SO4 and dil NaOH, Hydrogen gas is liberated at cathodes and oxygen gas is liberated at anode.
Answer the following questions:
Question 1.
Cut a lemon into two equal parts. Take the juice of each part into two separate beakers. Pour 10 ml of drinking water in one beaker and 20 ml in the second. Stir the solutions in both the beakers and taste them. Is there any difference in the tastes of the solutions in the two beakers? What is that difference?
Answer:
Question 2.
Take a big test tube. Choose a rubber stopper in which a gas tube can be fitted. Take a few pieces of magnesium ribbon in the test tube and add some dilute HCl to it. Take a lighted candle near the end of the gas tube and observe. What did you observe?
Answer:
Question 3.
Take some water in a test tube and add a little red oxide (the primer used before painting iron articles) to it. Now add a small quantity of dilute HCl to it, shake the test tube and observe.
(a) Does the red oxide dissolve in water?
(b) What change takes place in the particles of red oxide on adding dilute HCl?
Answer:
(a) The chemical formula of red oxide is Fe2O3. It is insoluble in water.
(b) The water-insoluble red oxide reacts with HCl to produce a water-soluble salt FeCl3.
Question 4.
Fit a bent tube in a rubber cork. Take some lime water in a test tube and keep it handy. Take some baking soda in another test tube and add some lemon juice to it. Immediately fit the bent tube over it. Insert its other end into the lime water. Note down your observations of both the test tubes. Repeat the procedure using washing soda, vinegar and dilute HC1 properly. What do you see?
Answer:
Class 9 Science Chapter 5 Acids, Bases and Salts Additional Important Questions and Answers
Select the correct option
Question 1.
…………………. acid is present in lemon.
(a) malic acid
(b) tartaric acid
(c) citric acid
(d) butyric acid
Answer:
(c) Citric acid
Question 2.
Tamarind contains …………………. acid.
(a) Lactic acid
(b) tartaric acid
(c) matlic acid
(d) butyric acid
Answer:
(b) tartaric
Question 3.
Butter milk contains …………………. acid.
(a) butyric acid
(b) Lactic acid
(c) matlic acid
(d) citric acid
Answer:
(a) Butyricacid
Question 4.
If the basic radical is H+ the type of compound is ………………… .
(a) neutral
(b) base
(c) acid
(d) alkali
Answer:
(c) Acid
Question 5.
The name of compound NH3 is ………………… .
(a) nitric acid
(b) ammonium
(c) nitride
(d) ammonia
Answer:
(b) ammonia
Question 6.
The bases which are soluble in water are called as ………………… .
(a) indicators
(b) acids
(c) alkalis
(d) salts
Answer:
(c) alkalis
Question 7.
H3PO4 is a …………………. acid.
(a) monobasic
(b) tribasic
(c) tetrabasic
(d) dibasic
Answer:
(b) tribasic
Question 8.
According to pH scale pure water has a pH of ………………… .
(a) 6
(b) 7
(c) 5
(d) 8
Answer:
(b) 7
Question 9.
With reference to neutralization, metallic oxides are ………………… in nature.
(a) basic
(b) neutral
(c) acidic
(d) saline
Answer:
(a) basic
Question 10.
Molecular formula of blue vitriol is ………………… .
(a) CuSO3 5H2O
(b) CuSO4 4H2O
(c) CUSO3 4H2O
(d) CUSO4 5H2O
Answer:
(d) CUSO4 5H2O
Question 11.
Molecular formula of crystalline alum is ………………… .
(a) KSO4, AISO4, 24H2O
(b) K2SO4, ALSO4, 24H2O
(c) K2SO4, AL2(SO4)3, 24H2O
(d) KSO4, Al2(SO4)3, 24H2O
Answer:
(c) K2SO4, AL2(SO4)3, 24H2O
Question 12.
Molecular formula for sodium oxide is ………………… .
(a) Na2O
(b) NaO2
(c) NaO
(d) Na2O2
Answer:
(a) Na2O
Question 13.
H2CO3 is …………………. acid.
(a) monobasic
(b) dibasic
(c) tribasic
(d) tetrabasic
Answer:
(b) dibasic
Question 14.
Molecular formula of Red oxide is ………………… .
(a) Fe2O3
(b) CuO
(c) Fe3O4
(d) Na2O
Answer:
(a) Fe2O3
Question 15.
The positive terminal electrode is called as ………………… .
(a) anode
(b) cathode
(c) anion
(d) cation
Answer:
(a) anode
Question 16.
…………………. produced in stomach helps in digestion.
(a) Hydrochloric acid
(b) Oxalic acid
(c) Sulphuric acid
(d) Nitric acid?
Answer:
(a) Hydrochloric acid
Question 17.
The solution turns blue litmus red, its pH is likely to be ………………… .
(a) 7
(b) 4
(c) 14
(d) 9
Answer:
(b) 4
Question 18.
An ionic compound NaCl is formed by ………………… .
(a) Na+ and Cl–
(b) Na+ and Cl+
(c) Na– and Cl–
(d) Na– and Cl+
Answer:
(a) Na+ and Cl–
Question 19.
pH of strong acid is ………………… .
(a) 0
(b) 7
(c) 8
(d) 14
Answer:
(a) 0
Question 20.
HCl + NaOH → NaCl + H2O is a …………………. reaction.
(a) neutralization
(b) crystallisation
(c) electrolysis
(d) dissociation
Answer:
(a) neutralization
Question 21.
Adding water to acid is an …………………. reaction.
(a) endothermic
(b) exothermic
(c) neutralisation
(d) crystallisation
Answer:
(b) exothermic
Find the odd one out:
(a) Rose Petal, Turmeric, Phenolphthalein, Indigo.
Answer:
Phenolphthalein is odd one out as rest are natural indicators while phenolphthalein is a synthetic indicator.
(b) Lime water, Vinegar, Acetic acid, Tartaric acid.
Answer:
Lime water is odd one out as this is basic in nature while rest are acidic.
(c) NaHCO3, HCl, H2SO4, HNO3
Answer:
NaHCO3 is odd one out as it is base while rest are acids.
(d) Oxalic acid, Nitric acid, Citric acid, acetic acid.
Answer:
Nitric acid is odd one out as others are weak acids while Nitric acid is a strong acid.
(e) Crystalline, Liquid, Gases, Solid.
Answer:
Crystalline is odd one out as this is nature of a compound while others are physical states of compounds.
(f) Ca(OH)2, Mg (OH)2, NaOH, NH4OH.
Answer:
NaOH is odd one out even though all are bases but NaOH is highly soluble in water compared to others.
Name the following:
Question 1.
Name the three types of ionic compounds.
Answer:
The three types of ionic compounds are acids, bases and salts.
Question 2.
Name the two constituents of molecule of an ionic compound.
Answer:
Question 3.
Name any three acids with their molecular formula.
Answer:
Question 4.
Name any three bases with their molecular formula.
Answer:
Question 5.
Name any three salts with their molecular formula.
Answer:
Question 6.
Name any two strong acids.
Answer:
Question 7.
Name any two weak acids.
Answer:
Question 8.
Name any two strong bases.
Answer:
Question 9.
Name a weak base.
Answer:
Ammonium hydroxide – NH4OH
Question 10.
Name any two alkalis.
Answer:
Question 11.
Name any two acids with their basicity 1 (monobasic)
Answer:
Question 12.
Name any two acids with their basicity 2 (dibasic)
Answer:
Question 13.
Name any two acids with their basicity 3 (tribasic)
Answer:
Question 14.
Name any two bases with their acidity 1 (monoacidic)
Answer:
Question 15.
Name any two bases with their acidity 2 (diacidic)
Answer:
Question 16.
Name any two bases with their acidity 3 (triacidic)
Answer:
Question 17.
Name the two units to express the concentration of the solution.
Answer:
Match the columns:
Question 1.
| Column ‘A’ | Column ‘B’ |
| (1) HNO3 (2) H3PO4 (3) CH3COOH (4) H2CO3 |
(a) Acetic acid (b) Carbonic acid (c) Phosphoric acid (d) Nitric acid |
Answer:
(1-d),
(2- c),
(3 – a),
(4 – b)
Question 2.
| Column ‘A’ | Column ‘B’ |
| (1) NH4OH (2) Ca(OH)2 (3) Al(OH)3 (4) Ba(OH)2 |
(a) Aluminium Hydroxide (b) Barium Hydroxide (c) Calcium Hydroxide (d) Ammonium Hydroxide |
Answer:
(1-d),
(2- c),
(3 – a),
(4 – b)
Question 3.
| Column ‘A’ Solution | Column ‘B’ pH | ||
| (1) | Milk | (a) | 0 |
| (2) | Milk of Magnesia | (b) | 14 |
| (3) | 1 M HCl | (c) | 10.5 |
| (4) | 1 M NaOH | (d) | 6.5 |
Answer:
(1-d),
(2- c),
(3 – a),
(4 – b)
Question 4.
| Column ‘A’ | Column’B’ |
| (1) Urine (2) Apples (3) Orange (4) Butter |
(a) Butyric acid (b) Uric acid (c) Malic acid (d) Citric acid |
Answer:
(1 – b),
(2 – c),
(3 – d),
(4 – a)
Question 5.
| Column ‘A’ | Column ‘B’ |
| (1) Crystalline blue vitriol (2) Crystalline green vitriol (3) Crystalline (4) washing soda Crystalline alum |
(a) FeS04-7H20 (b) K2S04-A12(S04)3.24H20 (c) CuS04-5H20 (d) Na2CO310H2O |
Answer:
(1-c),
(2- a),
(3 – d),
(4 – b)
State whether the following statements are true or false and if false. Correct the false statement:
(1) The separation of H and CI in HCI is in absence of water.
(2) \(\mathrm{NaOH}_{(\mathrm{s})} \frac{\text { Water }}{\text { dissociation }}>\mathrm{Na}_{(\mathrm{aq})}^{+}+\mathrm{OH}_{(\mathrm{aq})}^{-}\)
(3) H2SO4 is a strong acid.
(4) NaC1 is an ionic compound.
(5) Turmeric is synthetic indicator.
(6) Metal + Dilute acid forms salt and water.
(7) Copper oxide is called red primer.
(8) Oxide of non-metal + Acid → Salt + Water.
(9) Zinc oxide reacts with sodium hydroxide to form sodium zincate.
(10) Al2O3 is an amphoteric oxide.
(11) Blue vitriol ZnSO4. 7H2O.
(12) Molecular formula for crystalline Ferrous sulphate is Fe5O4. 5H2O.
(13) NaCl in water does not conduct electricity.
(14) Phenolphthalein is colourless in base.
Answer:
(1) False. The separation of H+ and Cl– in HC1 is in presence of water.
(2) True
(3) True
(4) True
(5) False. Turmeric is a natural indicator.
(6) False. Metal + Dilute acid forms salt and hydrogen gas.
(7) False. Iron oxide is called red primer.
(8) False. Oxide of izan-metal + Base → Salt + Wafer.
(9) True
(10) True
(11) False. Blue Vitriol is CuSO4. 5H2O.
(12) False. Molecular formula for crystalline Ferrous sulphate is FeSO4. 7H2O.
(13) False. NaCl in water conducts electricity.
(14) False, Phenolphthalein is colourless in acid and pink in base.
Define the following:
Question 1.
Acid
Answer:
An acid is a substance which on dissolving in water gives rise to H ion as the only cation. For example, HC1, H2 SO4, H2CO3.
Question 2.
Base
Answer:
A base is a substance which on dissolving in water gives rise to the OW ion as the only anion. For, NaOH, Ca(OH)2
Question 3.
Strong Acid
Answer:
On dissolving in water, a strong acid dissociates almost completely, and the resulting aqueous solution contains mainly H ions and the concerned acidic radical. e.g. HC1, HBr, HNO3, H2SO4.
Question 4.
Weak Acid
Answer:
On dissolving in water a weak acid does not dissociate completely, and the resulting aqueous solution contains H+ ion and the concerned acidic radical in small proportion along with large proportion of the undissociated molecules of the acid, e.g., H2CO3 (Carbonic acid), CH3COOH (Acetic acid)
Question 5.
Strong Base
Answer:
On dissolving in water, a strong base dissociates almost completely and the resulting aqueous solution contains mainly OH ions and the concerned basic radicals, e.g. NaOH, KOH, Ca(OH)2, Na2O.
Question 6.
Weak Base
Answer:
On dissolving in water, a weak base does not dissociate completely and the resulting aqueous solution contains a small proportion of OH ions and the concerned basic radical along with a large proportion of undissociated molecules of the base. e.g. NH4 OH.
Question 7.
Alkali
Answer:
The bases which are highly soluble in water are called alkali, e.g. NaOH, KOH, NH3. Here, NaOH and KOH are strong alkalis while NH3 is a weak alkali.
Question 8.
Basicity of acids
Answer:
The number of H+ ions obtainable by the dissociation of one molecule of an acid is called its basicity.
Question 9.
Acidity of bases
Answer:
The number of OH ions obtainable by the dissociation of one molecule of a base is called its acidity.
Question 10.
Concentration of solute in the solution.
Answer:
The proportion of a solute in a solution is called the concentration of the solute in the solution.
Question 11.
Concentrated solution.
Answer:
When the concentration of a solute in its solution is high, it is a concentrated solution.
Question 12.
Dilute solution
Answer:
When the concentration of a solute in its solution is low, it is a dilute solution.
Question 13.
Neutralization
Answer:
A reaction in which an acid reacts with a base to form salt and water is called a neutalization reaction.
NaOH + HC1 → NaCl + H2O
Base + Acid → Salt + Water
Question 14.
Cathode
Answer:
The electrode connected to the negative terminal of a battery by means of a conducting wire is called a cathode.
Question 15.
Anode
Answer:
The electrode connected to the positive terminal of a battery by means of a conducting wire is called an anode.
Question 16.
Cations
Answer:
Cations are positively charged ions which are attracted towards negative electrode (cathode) when electricity is passed into a solution of an ionic compound.
Question 17.
Anions
Answer:
Anions are negatively charged ions which are attracted towards the positive electrode (anode) when electricity is passed into a solution of an ionic compound.
Question 18.
Electrolytic cell
Answer:
An assembly that consists of a container with an electrolyte and the electrodes dipped in it, is called an electrolytic cell.
Question 19.
Molarity of a solution
Answer:
The number of moles of the solute dissolved in one litre of the solution is called the molarity of that solution. The molarity of a solute is indicated by writing its molecular formula inside a square bracket for example [NaCl] = 1
Question 20.
Acid – base indicators
Answer:
Some natural and synthetic dyes show two different colours in acidic and basic solution, and such dyes are acid base indicators.
Explain the following chemical reactions with the help of balanced equations:
Question 1.
Magnesium reacts with dilute hydrochloric acid.
Answer:
When magnesium reacts with dilute hydrochloric acid, it forms magnesium chloride and hydrogen gas is liberated.
Question 2.
When copper reacts with nitric acid.
Answer:
When copper reacts with nitric acid, it forms copper nitrate and hydrogen gas is liberated.
Question 3.
When ferric oxide reacts with diluted hydrochloric acid.
Answer:
When Ferric oxide reacts with diluted hydrochloric acid, it forms ferric chloride and water.
Question 4.
When calcium oxide reacts with dilute hydrochloric acid.
Answer:
When calcium oxide reacts with dilute hydrochloric acid, it forms calcium chloride and water.
Question 5.
When Magnesium oxide reacts with dilute hydrochloric acid.
Answer:
When magnesium oxide reacts with dilute hydrochloric acid, it forms magnesium chloride and water.
Question 6.
When zinc oxide reacts with dilute hydrochloric acid.
Answer:
When zinc oxide reacts with dilute hydrochloric acid, it forms zinc chloride and water.
Question 7.
When aluminium oxide reacts with hydrogen fluoride
Answer:
When aluminium oxide reacts with hydrogen fluoride, it forms Aluminium fluoride arid water.
Question 8.
When carbon dioxide reacts with sodium hydroxide.
Answer:
When carbon dioxide reacts with Sodium hydroxide, it forms Sodium carbonate and water.
Question 9.
When carbon dioxide reacts with potassium hydroxide.
Answer:
When carbon dioxide reacts with potassium hydroxide, it forms potassium carbonate and water.
Question 10.
When sulphur trioxide reacts with sodium hydroxide.
Answer:
When sulphur trioxide reacts with sodium hydroxide, it forms sodium sulphate and water.
Question 11.
When calcium hydroxide reacts with carbon dioxide.
Answer:
When calcium hydroxide reacts with carbon dioxide, it forms calcium carbonate and water.
Question 12.
When sodium carbonate reacts with hydrochloric acid.
Answer:
When sodium carbonate reacts with hydrochloric acid, it forms sodium chloride, carbon dioxide and water.
Question 13.
When sodium carbonate reacts with sulphuric acid.
Answer:
When sodium carbonate reacts with sulphuric acid, it forms sodium sulphate, carbon dioxide and water.
Question 14.
When calcium carbonate reacts with nitric acid.
Answer:
When calcium carbonate reacts with nitric acid, it forms calcium nitrate, carbon dioxide and water.
Question 15.
When potassium carbonate reacts with sulphuric acid.
Answer:
When potassium carbonate reacts with sulphuric acid, it forms potassium sulphate, carbon dioxide and water.
Question 16.
When sodium bicarbonate reacts with hydrochloric acid. OR Dilute HC1 was poured on baking soda
Answer:
When sodium bicarbonate reacts with hydrochloric acid, it forms sodium chloride, carbon dioxide and water.
Question 17.
When potassium bicarbonate reacts with nitric acid.
Answer:
When potassium bicarbonate reacts with nitric acid, it forms potassium nitrate, carbon dioxide and water.
Question 18.
When sodium bicarbonate reacts with acetic acid.
Answer:
When sodium bicarbonate reacts with acetic acid, it forms sodium acetate, carbon dioxide and water.
Question 19.
When copper sulphate is heated.
Answer:
When copper sulphate is heated it loses it’s water of crystallization to form white anhydrous copper sulphate.
Question 20.
When Ferrous sulphate is heated.
Answer:
When ferrous sulphate is heated it loses its water of crystallization to form white anhydrous ferrous sulphate.
Q.2. (B)-3. Complete the following table.
Question 1.
Complete the following table.
Answer:
Complete the following reactions.
Question 1.
Answer:
Question 2.
Metal + Dilute acid → Salt + Hydrogen
Answer:
Question 3.
Metal oxide + Dilute acid → SaIt + Water
Answer:
Question 4.
Oxide of non-metal + base → salt + water
Answer:
Question 5.
Carbonate salt of metal + dilute acid → Another salt of metal + Carbon dioxide + water
Answer:
Question 6.
Bicarbonate salt of metal + dilute acid → Another salt of metal + carbon dioxide + water
Answer:
Give scientific reasons:
Question 1.
Ionic compound NaCl has very high stability.
Answer:
Question 2.
Ionic compound dissociates while forming an aqueous solution.
Answer:
Question 3.
Blue coloured copper sulphate crystals become colourless on heating.
Answer:
Question 4.
During electrolysis of water, a few drops of sulphuric acid are added to it.
Answer:
Question 5.
Glucose is a non-electrolyte.
Answer:
Question 6.
Pure water is a poor conductor of electricity but aqueous solution of sodium chloride conducts electricity.
Answer:
Question 7.
When carbon dioxide gas is passed through freshly prepared lime water, the limewater turns milky.
Answer:
Q.3.1. Answer the following:
Question 1.
Write down chemical equations for
(a) Zinc oxide reacts with sodium hydroxide
(b) Aluminium oxide reacts with sodium hydroxide.
Answer:
(a) When zinc oxide reacts with sodium hydroxide, it forms sodium zincate and water
(b) When Aluminium oxide reacts with sodium hydroxide, it forms sodium aluminate and water.
Question 2.
Can we call Al2O3 and ZnO acidic oxides on the basis of above reactions.
Answer:
Question 3.
Define ‘amphoteric oxides’ and give two examples.
Answer:
Question 4.
Take a solution of 1g copper sulphate in 50ml water in a 100 ml capacity beaker. Use a thick plate of copper as anode and a carbon rod as cathode. Arrange the apparatus as shown in the figure and pass an electric current through the circuit for some time. Do you see any changes?
Answer:
Q.3.5. Answer in brief:
Question 1.
What are acids, bases and salts?
Answer:
Question 2.
What is an ionic bond?
Answer:
Question 3.
Give examples to show that proportions of H+ and OH– ions in aqueous solution determines the properties of those solutions.
Answer:
The examples to show that proportions of H+ and OH– ions in aqueous solution determines the properties of those solutions are :
Question 4.
What is pH scale?
Answer:
Question 5.
Give the pH of following solutions.
Answer:
Question 6.
What is universal indicator? Which is the most accurate method of measuring the pH of a solution?
Answer:
Answer in detail:
Question 1.
Explain the Arrhenius theory of acids and bases.
Answer:
The Swedish scientist Arrhenius put forth a theory of acids and bases in the year 1887. This theory gives definitions of acids and bases as follows:
Acid : An acid is a substance which on dissolving in water gives rise to H ion as the only cation. For example, HCl, H2SO4, H2CO3
Base: Abase is a substance which on dissolving in water gives rise to the OH ion as the only anion, For example, NaOH, Ca(OH)2
Question 2.
Write a short note on Neutralization.
Answer:
Question 3.
Explain the water of Crystallization.
Answer:
Question 4.
Explain the conduction of electricity through solutions of ionic compounds
Answer: