Acids, Bases and Salts

2026MCQ·1 mark·Q19Acids, bases and indicators

An aqueous solution turns red litmus blue. Excess addition of which of the following solution would reverse the change?

1. (a) Sodium hydroxide
2. (b) Hydrochloric acid
3. (c) Baking soda
4. (d) Slaked lime

2026MCQ·1 mark·Q23How acids and bases react with metals

How will you protect yourself from the heat generated while diluting a concentrated acid?

1. (a) By adding acid to water with constant stirring.
2. (b) By adding water to acid with constant stirring.
3. (c) By adding water to acid followed by base.
4. (d) By adding base to acid with constant stirring.

2026Case based·1 mark·Q28(a)The pH scale and why it matters in everyday life

pH plays an important role in daily life; strength of acids and bases depends on the number of H^+ and OH^- ions produced; the pH scale predicts strength via hydrogen ion concentration. What type of indicator is used to predict how strong an acid or base is?

2026Case based·1 mark·Q28(b)The pH scale and why it matters in everyday life

pH scale predicts strength of acids and bases via hydrogen ion concentration. Three solutions A, B and C showed pH as 3, 5 and 7. Which solution has the highest concentration of H^+ ions?

2026Case based·2 marks·Q28(c)The pH scale and why it matters in everyday life

Strength of acids and bases depends on H^+ and OH^- ions produced. What are strong acids and weak acids?

2026Case based·2 marks·Q28(c-OR)The pH scale and why it matters in everyday life

pH plays an important role in daily life. OR alternative for (c): (i) Under what condition is rainwater called acid rain? (ii) In the following acids, identify weak acids: Nitric acid, hydrochloric acid, acetic acid, sulphuric acid, formic acid.

2026Very short answer·2 marks·Q25Common salt and the chemicals made from it

(a) A compound 'A' is used in soda-lime fire-extinguisher and decomposes on heating to form compound 'B'. Compound 'B' is used for removing permanent hardness of water. Identify 'A' and 'B'. (b) Write chemical formula of Plaster of Paris. At what temperature gypsum is heated to obtain Plaster of Paris?

2025MCQ·1 mark·Q4How acids and bases react with metals

Consider the following reactions : (i) Dilute hydrochloric acid reacts with sodium hydroxide. (ii) Magnesium oxide reacts with dilute hydrochloric acid. (iii) Carbon dioxide reacts with sodium hydroxide. It is found that in each case :

1. (a) Salt and water is formed.
2. (b) Neutral salts are formed.
3. (c) Hydrogen gas is formed.
4. (d) Acidic salts are formed.

2025MCQ·1 mark·Q3The pH scale and why it matters in everyday life

The following table shows the pH values of four solutions A, B, C and D on a pH scale (see figure: pH scale 1-14 with B at 7, C at 13, D at 3, A at 5). The solutions A, B, C and D respectively are of a :

1. (a) Strong acid, weak acid, neutral, strong base
2. (b) Weak acid, neutral, weak base, strong base
3. (c) Weak acid, neutral, strong base, weak base
4. (d) Weak acid, neutral, strong base, strong acid

2025Case based·1 mark·Q37(a)Common salt and the chemicals made from it

[Case: Seawater contains many dissolved salts; common salt is separated from these, deposits of solid rock salt (brown due to impurities) are mined like coal, and common salt is an important raw material for chemicals of daily use.] Write balanced chemical equations to show the products formed during electrolysis of brine.

2025Case based·1 mark·Q37(b)Common salt and the chemicals made from it

[Case: Seawater/common salt/rock salt as raw material for chemicals of daily use.] List two uses of any one product obtained during electrolysis of brine.

2025Case based·2 marks·Q37(c)(i)Common salt and the chemicals made from it

[Case: Seawater/common salt/rock salt as raw material for chemicals of daily use.] A mild non-corrosive basic salt 'A', used for faster cooking, is strongly heated to produce a compound 'B', that is used for removing permanent hardness of water. Identify A and B and also write the equation for the reaction that occurs when A is heated.

2025Case based·2 marks·Q37(c)(ii)Water of crystallisation

[Case: Seawater/common salt/rock salt as raw material for chemicals of daily use.] Define water of crystallisation. Give two examples of salts that have water of crystallisation.

2024Assertion-Reason·1 mark·Q17How acids and bases react with metals

Assertion (A): Hydrogen gas is not evolved when zinc reacts with nitric acid. Reason (R): Nitric acid oxidises the hydrogen gas produced to water and itself gets reduced. Select the correct answer from codes:

1. (a) Both A and R are true and R is the correct explanation of A.
2. (b) Both A and R are true, but R is not the correct explanation of A.
3. (c) A is true, but R is false.
4. (d) A is false, but R is true.

2024Short answer·3 marks·Q28The pH scale and why it matters in everyday life

(i) The pH of a sample of tomato juice is 4.6. How is this juice likely to be in taste? Give reason to justify your answer. (ii) How do we differentiate between a strong acid and a weak base in terms of ion-formation in aqueous solutions? (iii) The acid rain can make the survival of aquatic animals difficult. How?

2024MCQ·1 mark·Q5Water of crystallisation

Consider the following compounds: FeSO_4 ; CuSO_4 ; CaSO_4 ; Na_2CO_3. The compound having maximum number of water of crystallisation in its crystalline form in one molecule is:

1. (a) FeSO_4
2. (b) CuSO_4
3. (c) CaSO_4
4. (d) Na_2CO_3

2023MCQ·1 mark·Q1How acids and bases react with metals

In the experimental setup given below, it is observed that on passing the gas produced in the reaction in the solution 'X' the solution 'X' first turns milky and then colourless. The option that justifies the above stated observation is that 'X' is aqueous calcium hydroxide and

1. (a) it turns milky due to carbon dioxide gas liberated in the reaction and after sometime it becomes colourless due to formation of calcium carbonate.
2. (b) it turns milky due to formation of calcium carbonate and on passing excess of carbon dioxide it becomes colourless due to formation of calcium hydrogen carbonate which is soluble in water.
3. (c) it turns milky due to passing of carbon dioxide through it. It turns colourless as on further passing carbon dioxide, sodium hydrogen carbonate is formed which is soluble in water.
4. (d) the carbon dioxide liberated during the reaction turns lime water milky due to formation of calcium hydrogen carbonate and after some time it turns colourless due to formation of calcium carbonate which is soluble in water. [Setup shows dilute hydrochloric acid and sodium carbonate in a test tube, the evolved gas passed into solution 'X'.]

2023Short answer·3 marks·Q28The pH scale and why it matters in everyday life

(a) Suggest one remedial measure each to counteract the change in pH in human beings in following cases: (i) Production of too much acid in stomach during indigestion (ii) Stung by a honey bee / nettle leaves. (b) Fresh milk has a pH of 6. When it changes into curd will its pH increase or decrease? Why?

2023MCQ·1 mark·Q4The pH scale and why it matters in everyday life

The table below has information regarding pH and the nature (acidic/basic) of four different solutions. Which one of the options in the table is correct?

1. (a) Lemon juice / Colour of pH paper Orange / Approximate pH value 3 / Nature Basic.
2. (b) Milk of magnesia / Blue / 10 / Basic.
3. (c) Gastric juice / Red / 6 / Acidic.
4. (d) Pure water / Yellow / 7 / Neutral.

2023Very short answer·2 marks·Q21(a)Common salt and the chemicals made from it

(i) A compound 'X' which is prepared from gypsum has the property of hardening when mixed with proper quantity of water. Identify 'X' and write its chemical formula. (ii) State the difference in chemical composition between baking soda and baking powder.

2023MCQ·1 mark·Q6Common salt and the chemicals made from it

Select washing soda from the following:

1. (a) NaHCO_3
2. (b) Na_2CO_3.5H_2O
3. (c) Na_2CO_3.10H_2O
4. (d) NaOH