Acids, Bases and Salts Practice Questions

Correct answer: Household vinegar

Vinegar contains acetic acid, and a characteristic property of acids is that they turn blue litmus paper red. The other options are basic in nature and would either turn red litmus blue or have no effect on blue litmus.

Correct answer: Salt and water

In a neutralization reaction, the $H^+$ ions from the acid react with the $OH^-$ ions from the base to form water ($H_2O$). The remaining ions combine to form a salt, which is an ionic compound.

Correct answer: Hydrochloric acid

The gastric glands in the stomach wall secrete Hydrochloric acid (HCl). This creates an acidic medium which facilitates the action of the enzyme pepsin and kills bacteria ingested with food.

Correct answer: 7

The pH scale ranges from 0 to 14, where 7 represents a neutral solution like pure water. Values below 7 indicate acidity, while values above 7 indicate alkalinity.

Correct answer: Soapy or slippery to the touch

Bases are characterized by a bitter taste and a slippery, soapy feel. They also turn red litmus blue and turn phenolphthalein indicator pink.

Correct answer: Carbon dioxide

Acids react with metal carbonates or metal hydrogen carbonates to produce a salt, water, and carbon dioxide gas. The evolution of $CO_2$ can be tested by passing it through limewater, which turns milky.

Correct answer: Nitric acid

Nitric acid ($HNO_3$) is a strong acid because it completely dissociates into its ions in an aqueous solution. Acetic, citric, and tartaric acids are organic acids that only partially ionize, making them weak acids.

Correct answer: Sodium hydrogen carbonate

Baking soda is Sodium hydrogen carbonate ($NaHCO_3$). It is a mild non-corrosive basic salt that releases carbon dioxide when heated or mixed with an acid, causing bread and cakes to rise.

Correct answer: Phenolphthalein

Phenolphthalein is a synthetic indicator used in titrations. It is colorless in acidic and neutral media but changes to a distinct pink/magenta color in solutions with a pH above 8.2.

Correct answer: Acidic

The pH of a salt solution depends on the strength of the parent acid and base. A salt from a strong acid and a weak base undergoes hydrolysis to produce an excess of $H^+$ ions, resulting in an acidic solution (pH < 7).

Correct answer: Washing soda

Washing soda (Sodium carbonate) is an important industrial chemical. It is used in glass, soap, and paper industries and also for removing the permanent hardness of water.

Correct answer: Methanoic acid

Ant stings contain Methanoic acid (also known as Formic acid). Rubbing a mild base like baking soda or calamine solution on the affected area can neutralize the acid and provide relief.

Correct answer: $CaOCl_2$

Bleaching powder is Calcium oxychloride ($CaOCl_2$), produced by the action of chlorine gas on dry slaked lime. It is used for bleaching cotton and linen in the textile industry and for disinfecting drinking water.

Correct answer: White

Heating hydrated copper sulfate removes the water of crystallization, turning the blue crystals into anhydrous copper sulfate, which is white. If water is added back, the blue color reappears.

Correct answer: Plaster of Paris

Plaster of Paris is a white powder that, on mixing with water, changes to Gypsum, forming a hard solid mass that holds bones in place.

Correct answer: It decreases per unit volume.

Dilution involves adding more solvent (water), which increases the total volume of the solution. This results in a decrease in the concentration of hydroxide ions ($OH^-$) per unit volume, though the total amount of ions remains the same.

Correct answer: A proton acceptor

The Brønsted-Lowry theory defines an acid as a proton ($H^+$) donor and a base as a proton acceptor. This is broader than the Arrhenius definition as it applies to reactions not occurring in aqueous solutions.

Correct answer: Vanilla essence

Olfactory indicators are substances whose odor changes in acidic or basic media. Vanilla, onion, and clove oil are examples used to test for acids and bases by people with visual impairments.

Correct answer: It mixes concentrated $HCl$ and $HNO_3$ in a 3:1 ratio.

Aqua Regia (Latin for 'royal water') is a freshly prepared mixture of concentrated hydrochloric acid and concentrated nitric acid in a 3:1 ratio by volume. The nitric acid oxidises the metal, while chloride ions from the hydrochloric acid tie up the metal ions as a stable complex, so gold and platinum dissolve even though neither acid attacks them on its own.

Correct answer: Caustic soda

Sodium hydroxide ($NaOH$) is commonly known as Caustic Soda. It is a strong base used in the manufacture of soaps, detergents, and as a laboratory reagent.