Question 1

1. A solution X has a hydrogen ion concentration of $10^{-4} mol/L$. What is the pH of this solution and its nature?

A) pH = 10, BasicB) pH = 4, BasicC) pH = 4, AcidicD) pH = -4, Acidic

Answer

✓ Correct Answer: Option C

Explanation: Solution: The pH of a solution is calculated using the formula: $$pH = -\log_{10}[H^+]$Given[H^+] = 10^{-4}, we have:$pH = -\log_{10}(10^{-4}) = -(-4) = 4$Since thepH < 7$, the solution is Acidic.

Question 2

2. When Zinc granules are treated with dilute sulfuric acid ($H_2SO_4$), which gas is evolved and how can it be tested?

A) Hydrogen gas; burns with a pop soundB) Oxygen gas; rekindles a glowing splint

Question 3

3. An aqueous solution turns red litmus paper blue. The pH of this solution is likely to be:

A) 4B) 10C) 1D) 5

Answer

✓ Correct Answer: Option B

Explanation: Solution: Bases turn red litmus blue. On the pH scale (0 to 14), acidic solutions have pH < 7, neutral solutions have pH = 7, and basic solutions have pH > 7. Among the options, only 10 is greater than 7.

Question 4

4. Calcium phosphate is present in tooth enamel. Its nature is:

A) AcidicB) NeutralC) AmphotericD) Basic

Answer

✓ Correct Answer: Option D

Explanation: Solution: Calcium phosphate ($Ca_3(PO_4)_2$) is a salt of a strong base (Calcium hydroxide) and a weak acid (Phosphoric acid). Therefore, its nature is Basic. This is why tooth decay starts when the pH in the mouth falls below 5.5 (becoming more acidic).

Question 5

5. What is the chemical formula for Bleaching Powder?

A) $Ca(OH)_2$B) $CaOCl_2$C) $CaCl_2$D) $CaCO_3$

Answer

✓ Correct Answer: Option B

Explanation: Solution: Bleaching powder is produced by the action of chlorine on dry slaked lime: $$Ca(OH)_2 + Cl_2 \rightarrow CaOCl_2 + H_2O$The chemical name is Calcium Oxychloride, and its formula is CaOCl_2$.

Question 6

6. Which of the following is the correct reaction for the preparation of Baking Soda?

A) $NaCl + H_2O + CO_2 + NH_3 \rightarrow NH_4Cl + NaHCO_3$B) $2NaCl + H_2O + CO_2 \rightarrow Na_2CO_3 + 2HCl$C) $NaOH + CO_2 \rightarrow NaHCO_3$D) $Na_2CO_3 + H_2O \rightarrow 2NaOH + CO_2$

Answer

✓ Correct Answer: Option A

Explanation: Solution: Baking soda (Sodium hydrogen carbonate) is produced using the Solvay process where Sodium Chloride reacts with water, carbon dioxide, and ammonia: $$NaCl + H_2O + CO_2 + NH_3 \rightarrow NH_4Cl + NaHCO_3$$

Question 7

7. If a solution A has a pH of 2 and solution B has a pH of 6, which solution has a higher concentration of $H^+$ ions and by what factor?

A) Solution B is $10^4$ times more acidic than AB) Solution A is 4 times more acidic than BC) Solution A is $10^4$ times more acidic than BD) Solution B is 4 times more acidic than A

Answer

✓ Correct Answer: Option C

Explanation: Solution: We know $[H^+] = 10^{-pH}$. For solution A: $[H^+]_A = 10^{-2} mol/L$ For solution B: $[H^+]_B = 10^{-6} mol/L$ Ratio: $$\frac{[H^+]_A}{[H^+]_B} = \frac{10^{-2}}{10^{-6}} = 10^{-2 - (-6)} = 10^4 = 10,000$Thus, Solution A is 10,000 (or10^4$) times more acidic than Solution B.

Question 8

8. Which substance is used for softening hard water?

A) Baking SodaB) Washing SodaC) Bleaching PowderD) Plaster of Paris

Answer

✓ Correct Answer: Option B

Explanation: Solution: Sodium carbonate ($Na_2CO_3 \cdot 10H_2O$), commonly known as Washing Soda, is used in glass, soap, and paper industries and is specifically used for removing permanent hardness of water.

Question 9

9. When Gypsum is heated to 373 K, it loses water molecules and becomes:

A) Slaked LimeB) Quick LimeC) Anhydrous Calcium SulfateD) Plaster of Paris

Answer

✓ Correct Answer: Option D

Explanation: Solution: On heating Gypsum ($CaSO_4 \cdot 2H_2O$) at 373 K ($100^{\circ}C$), it loses water molecules to form Calcium Sulfate Hemihydrate ($CaSO_4 \cdot \frac{1}{2}H_2O$), which is Plaster of Paris.

Question 10

10. An ant's sting contains which acid that causes pain and irritation?

A) Methanoic AcidB) Acetic AcidC) Citric AcidD) Tartaric Acid

Answer

✓ Correct Answer: Option A

Explanation: Solution: Ant stings and nettle stings inject Methanoic acid (also known as Formic acid) into the skin, causing a burning sensation. This can be neutralized by rubbing a mild base like baking soda.

Accepted Answer

✓ Correct Answer: Option A

Explanation: Solution: Metals react with dilute acids to produce hydrogen gas and a salt: $$Zn(s) + H_2SO_4(aq) \rightarrow ZnSO_4(aq) + H_2(g)$$ Hydrogen gas is colorless and odorless, and it burns with a characteristic pop sound when a burning candle is brought near the mouth of the test tube.

Grade 10 : Science - 2. Acids/Bases (Set 1)

1. A solution X has a hydrogen ion concentration of $10^{-4} mol/L$. What is the pH of this solution and its nature?

2. When Zinc granules are treated with dilute sulfuric acid ($H_2SO_4$), which gas is evolved and how can it be tested?

3. An aqueous solution turns red litmus paper blue. The pH of this solution is likely to be:

4. Calcium phosphate is present in tooth enamel. Its nature is:

5. What is the chemical formula for Bleaching Powder?

6. Which of the following is the correct reaction for the preparation of Baking Soda?

7. If a solution A has a pH of 2 and solution B has a pH of 6, which solution has a higher concentration of $H^+$ ions and by what factor?

8. Which substance is used for softening hard water?

9. When Gypsum is heated to 373 K, it loses water molecules and becomes:

10. An ant's sting contains which acid that causes pain and irritation?