Science Olympiad Test: Acids, Bases and Salts- 2 - Free MCQ with solutions

Turning of the pH paper yellowish – orange shows that the solution is acidic (pH ≈ 5) . To change it to greens blue means we want to change it to basic (pH ≈ 8) This can be done by adding an antacid [like Mg(OH)₂)]

Mixing of solution of an acid with the solution of base (neutralization) is exothermic i.e. temperature increase and salt formation takes place.

Glauber’s salt is sodium sulphate decahydrate Na₂SO₄.10H₂O

Green vitriol or ferrous sulphate is FeSO₄.7H₂O

• If a few drops of a concentrated acid accidentally spill over the hand of a student, wash the hand immediately with plenty of water and apply a paste of sodium hydrogen carbonate.
• Water will dilute the acid and wash it out. Any remaining acid will be neutralized with sodium hydrogen carbonate. This will minimize the effect of acid and damage to the skin.

HCl has the highest acidic strength as it is a strong acid and completely or 100% ionizes into its ions which is shown by its dissociation constant. Acetic acid partially dissociates into its ions and at equilibrium stage both the ions, acetae and hydrogen ions are present so it has less acidic strength than HCl. Water is the weakest of all and its ions hydrogen and hydroxide ions keeps on forming water molecule at the equilibrium stage.

Calcium phosphate is basic salt since it is a source of weak phosphoric acid and a slightly stronger base of calcium hydroxide. Calcium phosphate is a mineral comprising calcium ion (Ca²⁺) and phosphate ion which is inorganic in nature.  It is present in the crown area of the tooth and also in bones.

pH = 4 means [H⁺] = 10^–4 M. pH = 10 means (H⁺) = 10^–10 M or [H^–] = 10^–4 M
Thus, one solution is acidic and the other is basic. Further, they have same molarity. On mxing equal volumes, then will neutralize each other completely. The resulting solution will be neutral with pH = 7.0

C₂H₅OH is alcohol, not a base. An acid is any hydrogen-containing substance that is capable of donating a proton (hydrogen ion) to another substance.  A base is a molecule or ion able to accept a hydrogen ion from an acid.

• The acid used in eye wash is boric acid.
• Boric acid is a mild antiseptic, insecticide and its chemical formula is H₃BO₃^.
• It has antibiotic properties against bacterial infection.
• It is used as a cleanser for the eyes.

HCl + H₂O → H₃O⁺ + Cl^–
In the aqueous solution of HCl hydronium ions are formed along with chloride ions.

Cupric ions, as they react with excess of ammonia solution to form [Cu(NH₃)₄]²⁺

When dilute hydrochloric acid is poured over powdered calcium carbonate, efflorescence are formed, it is because carbon dioxide is evolved.

pH = – log [H⁺]
pH = – log (1 × 10^–3] = – (– 3) log₁₀
pH = 3

Marble, Limestone and baking soda have carbonates which produces CO₂ gas. Lime contains Hydroxide which will not produce CO_2. Marble, limestone, and baking soda are all metal carbonates or bicarbonates. When they interact with a dilute acid, carbon dioxide is produced. When lime, which is calcium oxide, combines with a dilute acid carbon dioxide is not produced.
CaO + dil 2HCl → CaCl₂ + H₂O
Thus, lime when reacts with an acid then it produces salt and water but it does not produce carbon dioxide.