Acids & Bases: HOTS Mastery (Set 3)

1. A student dilutes a solution of hydrochloric acid ($HCl$) with a $pH$ of $3.0$ by adding enough distilled water to increase the total volume by $100$ times. What will be the approximate $pH$ of the resulting solution?

A) $pH = 1.0$

B) $pH = 4.0$

C) $pH = 5.0$

D) $pH = 7.0$

2. An unknown substance $P$ reacts with granulated zinc to evolve a gas that burns with a 'pop' sound. The same substance $P$ turns phenolphthalein solution pink. Identify $P$.

A) Sodium Hydroxide ($NaOH$)

B) Ethanoic Acid ($CH_3COOH$)

C) Hydrochloric Acid ($HCl$)

D) Sodium Chloride ($NaCl$)

3. Consider two acids: Acid $A$ ($0.1M$) and Acid $B$ ($0.1M$). Acid $A$ conducts more electricity than Acid $B$. Which of the following statements is logically correct?

A) Acid $B$ is a stronger acid than Acid $A$.

B) Acid $A$ has a higher concentration of $H^+$ ions than Acid $B$.

C) Acid $A$ has a higher $pH$ value than Acid $B$.

D) Both acids are equally ionized in the solution.

4. A solution of a base $X$ is used to treat a wasp sting, which is alkaline in nature. However, the patient experiences more irritation. This implies the sting was likely from a honeybee. Which substance should have been used instead?

A) Concentrated $H_2SO_4$

B) $NaOH$ solution

C) Distilled water

D) Mild base like $NaHCO_3$

5. In the Chlor-alkali process, if the gas evolved at the anode is $G_1$ and the gas at the cathode is $G_2$, which statement correctly identifies their primary industrial uses?

A) $G_1$ (Oxygen) is used for steel manufacturing.

B) $G_1$ (Chlorine) is used for water treatment and PVC.

C) $G_2$ (Chlorine) is used for making bleaching powder.

D) $G_2$ (Nitrogen) is used for making ammonia.

6. Calculate the number of water molecules lost when $1$ mole of Gypsum is heated at $373 K$ to form Plaster of Paris.

A) $0.5$ molecules

B) $1.0$ molecule

C) $1.5$ molecules

D) $2.0$ molecules

7. A dry pellet of a common base $M$, when kept in the open, absorbs moisture and turns sticky. The compound is also a byproduct of the Chlor-alkali process. Identify $M$.

A) $NaOH$

B) $Ca(OH)_2$

C) $KOH$

D) $NaHCO_3$

8. Which of the following correctly describes the nature of the oxide formed when Magnesium burns in air, and its subsequent reaction with water?

A) Acidic oxide; turns red litmus blue.

B) Acidic oxide; turns blue litmus red.

C) Basic oxide; turns red litmus blue.

D) Neutral oxide; no change in litmus.

9. If the $pH$ of a soil sample is $4.5$, which of the following substances should a farmer add to the soil to neutralize the acidity for better crop growth?

A) Ammonium Sulfate

B) Common Salt ($NaCl$)

C) Vinegar

D) Quicklime ($CaO$)

10. An aqueous solution of Sodium Carbonate ($Na_2CO_3$) is:

A) Acidic because it is a salt of a strong acid and weak base.

B) Basic because it is a salt of a weak acid and strong base.

C) Neutral because it is a salt of a strong acid and strong base.

D) Weakly acidic because of atmospheric $CO_2$.