CBSE Class 10 Science Acids Bases and Salts VBQs Set 04

Question. Which of the following phenomena occur, when a small amount of acid is added to water ?
(i) Ionisation
(ii) Neutralisation
(iii) Dilution
(iv) Salt formation
(a) (i) and (ii)
(b) (i) and (iii)
(c) (ii) and (iii)
(d) (ii) and (iv)
Answer: (b) (i) and (iii)

Question. Which one of the following can be used as an acid-base indicator by a visually impared (blind) student?
(a) Litmus
(b) Turmeric
(c) Vanilla essence
(d) Petunia leaves
Answer: (c) Vanilla essence

Question. Which of the following is used for dissolution of gold?
(a) Hydrochloric acid
(b) Sulphuric acid
(c) Nitric acid
(d) Aqua regia
Answer: (d) Aqua regia

Question. Which among the following is not a base ?
(a) \( NaOH \)
(b) \( KOH \)
(c) \( NH_4OH \)
(d) \( C_2H_5OH \)
Answer: (d) \( C_2H_5OH \)

Question. Which of the following statement is not correct?
(a) All metal carbonates react with acid to give salt, water and carbon dioxide.
(b) All metal oxides react with water to give salt and acid.
(c) Some metals react with acids to give salt and hydrogen.
(d) Some non-metal oxides react with water to form an acid.
Answer: (b) All metal oxides react with water to give salt and acid.

Question. Which of the following is(are) true when \( HCl \) (g) is passed through water?
(i) It does not ionise in the solution as it is a covalent compound.
(ii) It ionises in the solution.
(iii) It gives both hydrogen and hydroxyl ion in the solution.
(iv) It forms hydronium ion in the solution due to the combination of hydrogen ion with water molecule.
(a) (i) only
(b) (iii) only
(c) (ii) and (iv)
(d) (iii) and (iv)
Answer: (c) (ii) and (iv)

Question. Which of the following statements is true for acids?
(a) Bitter and change red litmus to blue.
(b) Sour and change red litmus to blue.
(c) Sour and change blue litmus to red.
(d) Bitter and change blue litmus to red.
Answer: (c) Sour and change blue litmus to red.

Question. Which of the following are present in a dilute aqueous solution of hydrochloric acid?
(a) \( H_3O^+ + Cl^- \)
(b) \( H_3O^+ + OH^- \)
(c) \( Cl^- + OH^- \)
(d) unionised \( HCl \)
Answer: (a) \( H_3O^+ + Cl^- \)

Question. Sodium hydrogen carbonate when added to acetic acid evolves a gas. Which of the following statements are true about the gas evolved?
(i) It turns lime water milky
(ii) It extinguishes a burning splinter
(iii) It dissolves in a solution of sodium hydroxide
(iv) It has a pungent odour
(a) (i) and (ii)
(b) (i), (ii) and (iii)
(c) (ii), (iii) and (iv)
(d) (i) and (iv)
Answer: (b) (i), (ii) and (iii)

Question. Common salt, besides being used in kitchen, can also be used as the raw material for making
(i) washing soda
(ii) bleaching powder
(iii) baking soda
(iv) slaked lime
(a) (i) and (ii)
(b) (i), (ii) and (iv)
(c) (i) and (iii)
(d) (i), (iii) and (iv)
Answer: (c) (i) and (iii)

Question. Which of the following statements is correct about an aqueous solution of an acid and of a base ?
(i) Higher the pH, stronger the acid
(ii) Higher the pH, weaker the acid
(iii) Lower the pH, stronger the base
(iv) Lower the pH, weaker the base
(a) (i) and (iii)
(b) (ii) and (iii)
(c) (i) and (iv)
(d) (ii) and (iv)
Answer: (d) (ii) and (iv)

Question. The pH of the gastric juices released during digestion is
(a) less than 7
(b) more than 7
(c) equal to 7
(d) equal to 0
Answer: (a) less than 7

Question. Which of the following substance will not give carbon dioxide on treatment with dilute acid ?
(a) Marble
(b) Limestone
(c) Baking soda
(d) Lime
Answer: (d) Lime

Question. Which of the following is not a mineral acid ?
(a) Hydrochloric acid
(b) Citric acid
(c) Sulphuric acid
(d) Nitric acid
Answer: (b) Citric acid

Question. Identify the correct representation of reaction occurring during chloralkali process.
(a) \( 2NaCl(l) + 2H_2O(l) \rightarrow 2NaOH(l) + Cl_2 (g) + H_2 (g) \)
(b) \( 2NaCl (aq) + 2H_2O(aq) \rightarrow 2NaOH(aq) + Cl_2 (g) + H_2 (g) \)
(c) \( 2NaCl (aq) + 2H_2O(l) \rightarrow 2NaOH (aq) + Cl_2 (aq) + H_2 (aq) \)
(d) \( 2NaCl (aq) + 2H_2O(l) \rightarrow 2NaOH(aq) + Cl_2 (g) + H_2 (g) \)
Answer: (d) \( 2NaCl (aq) + 2H_2O(l) \rightarrow 2NaOH(aq) + Cl_2 (g) + H_2 (g) \)

Question. Match the important chemicals given in Column (A) with the chemical formulae given in Column (B).
Column (A) | Column (B)
(a) Plaster of Paris | (i) \( Ca(OH)_2 \)
(b) Gypsum | (ii) \( CaSO_4 \cdot \frac{1}{2} H_2O \)
(c) Bleaching Powder | (iii) \( CaSO_4 \cdot 2H_2O \)
(d) Slaked Lime | (iv) \( CaOCl_2 \)
Answer: (a) — (ii), (b) — (iii), (c) — (iv), (d) — (i)

Question. What will be the action of the following substances on litmus paper?
Dry \( HCl \) gas, Moistened \( NH_3 \) gas, Lemon juice, Carbonated soft drink, Curd, Soap solution.
Answer: Dry \( HCl \) gas will not have any effect on litmus paper. Moistened \( NH_3 \) gas will turn red litmus blue. Curd, lemon juice, carbonated soft drink will turn blue litmus red. Soap solution will turn red litmus blue.

Question. Name the acid present in ant sting and give its chemical formula. Also give the common method to get relief from the discomfort caused by the ant sting.
Answer: Ant sting contains methanoic acid (formic acid). Its chemical formula is \( HCOOH \). The common method to get relief is to apply paste of \( NaHCO_3 \) (baking soda) on it.

Question. What happens when nitric acid is added to egg-shell?
Answer: Egg-shell is made up of calcium carbonate which will react with \( HNO_3 \) to form \( CO_2 (g) \) and \( H_2O (l) \) along with calcium nitrate, e.g.
\( CaCO_3 + 2HNO_3 \rightarrow Ca(NO_3)_2 + CO_2 + H_2O \)

Question. A student prepared solutions of (i) an acid and (ii) a base in two separate beakers. She forgot to label the solutions and litmus paper is not available in the laboratory. Since, both the solutions are colourless, how will she distinguish between the two? 
Answer: Add phenolphthalein to a portion of each solution in separate test tube. If it turns pink, the beaker contains base whereas if it remains colourless, it is an acid. If phenolphthalein is not available, pH paper can be used. Acid will turn pH paper red, base will turn pH paper blue.

Question. In one of the industrial processes used for manufacture of sodium hydroxide, a gas X is formed as by-product. The gas X reacts with lime water to give a compound Y which is used as a bleaching agent in chemical industry. Identify X and Y giving the chemical equation of the reactions involved. 
Answer: ‘X’ is chlorine gas.
\( 2NaCl + 2H_2O \xrightarrow{Electricity} 2NaOH + H_2(g) + Cl_2(g) \)
‘X’ is \( Cl_2 \).
\( Ca(OH)_2 + Cl_2(g) \rightarrow CaOCl_2 + H_2O \)
Lime water ‘Y’ Bleaching powder
‘Y’ is \( CaOCl_2 \).

Question. Fill in the missing data in the following table:
Name of the salt | Formula | Salt obtained from Base | Salt obtained from Acid
(i) Ammonium chloride | \( NH_4Cl \) | \( NH_4OH \) | —
(ii) Copper sulphate | — | — | \( H_2SO_4 \)
(iii) Sodium chloride | \( NaCl \) | \( NaOH \) | —
(iv) Magnesium nitrate | \( Mg(NO_3)_2 \) | — | \( HNO_3 \)
(v) Potassium sulphate | \( K_2SO_4 \) | — | —
(vi) Calcium nitrate | \( Ca(NO_3)_2 \) | \( Ca(OH)_2 \) | —
Answer: (i) Acid: \( HCl \) 
(ii) Formula: \( CuSO_4 \); Base: \( Cu(OH)_2 \)
(iii) Acid: \( HCl \)
(iv) Base: \( Mg(OH)_2 \)
(v) Base: \( KOH \); Acid: \( H_2SO_4 \)
(vi) Acid: \( HNO_3 \) 

Question. A metal carbonate X on reacting with an acid gives a gas which when passed through a solution Y gives the carbonate back. On the other hand, a gas G that is obtained at anode during electrolysis of brine is passed on dry Y, it gives a compound Z, used for disinfecting drinking water. Identify X, Y, G and Z. 
Answer: ‘X’ is calcium carbonate.
\( CaCO_3(s) + 2HCl(dil) \rightarrow CaCl_2(aq) + CO_2(g) + H_2O(l) \)
\( Ca(OH)_2 + CO_2 \rightarrow CaCO_3(s) + H_2O \)
‘Y’ is calcium hydroxide.
\( 2NaCl + 2H_2O \rightarrow 2NaOH + Cl_2(g) + H_2(g) \)
(At anode) ‘G’ is chlorine gas.
\( Ca(OH)_2 + Cl_2 \rightarrow CaOCl_2 + H_2O \)
‘Y’ ‘G’ ‘Z’
‘Z’ is calcium oxychloride used for disinfecting drinking water.

Question. A sulphate salt of Group 2 element of the Periodic Table is a white, soft substance, which can be moulded into different shapes by making its dough. When this compound is left in open for sometime, it becomes a solid mass and cannot be used for moulding purposes. Identify the sulphate salt. Why does it show such a behaviour? Give the reaction involved.
Answer: Salt is \( CaSO_4 \cdot \frac{1}{2} H_2O \), Plaster of Paris, white soft substance. It can be dough, moulded into different shapes, as 2 moles of \( CaSO_4 \) share 1 mole of \( H_2O \) molecule.
\( CaSO_4 \cdot \frac{1}{2} H_2O + 1 \frac{1}{2} H_2O \rightarrow CaSO_4 \cdot 2H_2O \)
When it is left in open, it becomes solid mass \( CaSO_4 \cdot 2H_2O \) (Gypsum) which cannot be used for moulding purposes as it is hard solid mass.

Question. Identify the compound X on the basis of the reactions given below. Also, write the name and chemical formulae of A, B and C. 
Compound ‘X’ + \( Zn \rightarrow A + H_2(g) \)
Compound ‘X’ + \( HCl \rightarrow B + H_2O \)
Compound ‘X’ + \( CH_3COOH \rightarrow C + H_2O \)
Answer: ‘X’ is \( NaOH \).
\( 2NaOH + Zn \rightarrow Na_2ZnO_2 + H_2(g) \)
‘X’ ‘A’ is Sodium zincate
\( NaOH + HCl \rightarrow NaCl + H_2O \)
‘X’ ‘B’ is Sodium chloride
\( NaOH + CH_3COOH \rightarrow CH_3COONa + H_2O \)
‘X’ ‘C’ is Sodium ethanoate

Question. Which acid is used in lead storage car batteries?
(a) \( HCl \)
(b) \( HNO_3 \)
(c) \( H_2SO_4 \)
(d) \( CH_3COOH \)
Answer: (c) \( H_2SO_4 \)

Question. Which of the following has highest concentration of \( OH^- \)?
(a) pH = 3
(b) pH = 5
(c) pH = 7
(d) pH = 12
Answer: (d) pH = 12

Question. Which of the following does not react with dilute \( HCl \) and liberate \( H_2 \) gas?
(a) Mg
(b) Cu
(c) Zn
(d) Fe
Answer: (b) Cu

Question. Mg liberates \( H_2(g) \) with
(a) \( HCl \)
(b) \( H_2SO_4(dil.) \)
(c) \( HNO_3(5\%) \)
(d) All of the options
Answer: (d) All of the options

Direction: In the following Questions, the Assertion and Reason have been put forward. Read the statements carefully and choose the correct alternative from the following:
(a) Both the Assertion and the Reason are correct and the Reason is the correct explanation of the Assertion.
(b) The Assertion and the Reason are correct but the Reason is not the correct explanation of the Assertion.
(c) Assertion is true but the Reason is false.
(d) The statement of the Assertion is false but the Reason is true.

Question. Assertion: Gold and platinum are soluble in aqua regia.
Reason: Aqua regia containing conc. \( HCl \) and conc. \( HNO_3 \) in ratio of 3 : 1.
(a) A
(b) B
(c) C
(d) D
Answer: (a)

Question. Assertion: Sodium acetate is basic salt.
Reason: It is because it is salt of weak acid \( (CH_3COOH) \) and strong base \( (NaOH) \)
(a) A
(b) B
(c) C
(d) D
Answer: (a)

Question. Write product of electrolysis of brine solution. Write products at cathode and anode.
Answer: The products of electrolysis of brine (concentrated aqueous \( NaCl \) solution) are Sodium Hydroxide (\( NaOH \)), Chlorine gas (\( Cl_2 \)), and Hydrogen gas (\( H_2 \)).
At anode: Chlorine gas (\( Cl_2 \)) is evolved.
At cathode: Hydrogen gas (\( H_2 \)) is evolved.
Sodium hydroxide solution is formed near the cathode.

Question. How do we prepare plaster of paris from Gypsum? Give one of its use.
Answer: Plaster of Paris is prepared by heating Gypsum \( (CaSO_4 \cdot 2H_2O) \) at a temperature of 373 K. On heating, it loses water molecules and becomes calcium sulphate hemihydrate.
\[ CaSO_4 \cdot 2H_2O \xrightarrow{373 K} CaSO_4 \cdot \frac{1}{2} H_2O + 1\frac{1}{2} H_2O \]
Use: It is used by doctors for supporting fractured bones in the right position.

Question. Complete the following:
(i) \( Ca(OH)_2 + Cl_2 \rightarrow \)
(ii) \( NaHCO_3 \xrightarrow{\Delta} \)
(iii) \( CaSO_4 \cdot 2H_2O \xrightarrow{373 K} \)
Answer:
(i) \( Ca(OH)_2 + Cl_2 \rightarrow CaOCl_2 + H_2O \)
(ii) \( 2NaHCO_3 \xrightarrow{\Delta} Na_2CO_3 + H_2O + CO_2 \)
(iii) \( CaSO_4 \cdot 2H_2O \xrightarrow{373 K} CaSO_4 \cdot \frac{1}{2} H_2O + 1\frac{1}{2} H_2O \)

Question. (a) How can be prepare dil. \( H_2SO_4 \) from conc. \( H_2SO_4 \)? Explain.
(b) What happens when conc. \( HNO_3 \) comes in contact with our skin? Give reason.
(c) Why should we avoid contact with conc. \( H_2SO_4 \)?
Answer:
(a) To prepare dilute \( H_2SO_4 \), concentrated sulphuric acid is added slowly to water with constant stirring. This is because the process of dilution is highly exothermic. Adding water to concentrated acid may cause the mixture to splash out.
(b) When concentrated \( HNO_3 \) comes in contact with skin, it produces yellow stains and burns. This is because it reacts with skin proteins to form xanthoproteic acid.
(c) We should avoid contact with concentrated \( H_2SO_4 \) because it is a strong dehydrating agent and highly corrosive, causing severe chemical burns on contact with tissues.

Question. Complete the following reaction:
(i) \( Mn + HNO_3(5\%) \rightarrow \)
(ii) \( NaOH + H_2CO_3 \rightarrow \)
(iii) \( CaCO_3 + HCl \rightarrow \)
(iv) \( Ca(OH)_2 + CO_2 \rightarrow \)
(v) \( Cu + HNO_3(dil.) \rightarrow \)
Answer:
(i) \( Mn + 2HNO_3(5\%) \rightarrow Mn(NO_3)_2 + H_2(g) \)
(ii) \( 2NaOH + H_2CO_3 \rightarrow Na_2CO_3 + 2H_2O \)
(iii) \( CaCO_3 + 2HCl \rightarrow CaCl_2 + H_2O + CO_2 \)
(iv) \( Ca(OH)_2 + CO_2 \rightarrow CaCO_3 + H_2O \)
(v) \( 3Cu + 8HNO_3(dil.) \rightarrow 3Cu(NO_3)_2 + 4H_2O + 2NO \uparrow \)

The table shows the results of different experiments conducted on two acids ‘X’ and ‘Y’ of equal concentration.
| Experiment | ‘X’ | ‘Y’ |
| :--- | :--- | :--- |
| Conductivity of solution | 400 | 7.00 |
| Rise in temperature on reaction with \( NaOH \) | 6.9°C | 6.7°C |
| Reaction with Mg | Hydrogen gas produced rapidly | \( H_2 \) gas produced slowly |

Question. Identify strength of ‘X’ and ‘Y’.
Answer: ‘X’ is a strong acid and ‘Y’ is a weak acid.

Question. Why is conductivity of ‘X’ higher than ‘Y’?
Answer: ‘X’ being a strong acid ionizes completely in aqueous solution, providing a higher concentration of ions to conduct electricity compared to the weak acid ‘Y’ which ionizes only partially.

Question. Name the reaction between ‘X’ and ‘Y’ with \( NaOH \). Is it exothermic or endothermic?
Answer: The reaction is called a Neutralization reaction. It is an exothermic reaction as indicated by the rise in temperature.

Question. What will be nature of salt formed between
(i) ‘X’ and \( NaOH \)
(ii) ‘Y’ and \( NaOH \)
Give reason.
Answer:
(i) The salt formed between ‘X’ (strong acid) and \( NaOH \) (strong base) will be neutral in nature because both completely neutralize each other.
(ii) The salt formed between ‘Y’ (weak acid) and \( NaOH \) (strong base) will be basic in nature because the strong base dominates the properties of the resulting salt.