Acid, Bases, and Indicators Questions and Answers - Form 1 to 4
QUESTION 1.
Explain why concentrated sulphuric acid is a weaker acid than dilute sulphuric acid?
ANSWER
Concentrated sulphuric acid is a covalent compound. Dilute sulphuric acid is an ionic compound. It ionizes fully producing more hydrogen ions (H+ )
QUESTION 2.
Explain the following observations. A molar solution of nitrous acid (Nitric (III) acid has a PH of 2 whereas one molar solution of hypochlorous acid (Chloric (I) acid has a PH of 4.
ANSWER
Nitrous acid ionizes more compared to hypochlorous acid. Hypochlorous acids is a very weak acids. It ionizes partially producing few hydrogen ions(H+ )
QUESTION 3.
Explain how you would distinguish between a carbonate and a sulphite using dilute acid and blue litmus paper.
ANSWER
Carbonate reacts with acid-producing carbon (IV) Oxide which is weaker acidic in presence of water. It changes litmus to pink. Sulphite on the other hand reacts with dilute acid producing sulphur (IV). Oxide is a strong acid in presence of water. It changes litmus to red.
QUESTION 4.
Describe how the following reagents can be used to prepare Lead sulphate, solid potassium sulphate, solid lead carbonate, dilute nitric acid and distilled water.
ANSWER
React Lead Carbonate with dilute Nitric acid to get a solution of lead Nitrate. PbCO3(s) + 2HNO3 → Pb(NO3)(aq) + H20(l) + CO2(g) Dissolve potassium sulphate in water to get its solution.
Mix potassium sulphate solution with Lead Nitrate Solution to obtain Lead Sulphate as a precipitate. Pb(NO3)2 + K2SO4(aq) → PbSO4(s) + 2KNO3(aq) Filter the resulting mixture to obtain Lead sulphate as a residue. Wash it with distilled water and dry it.
QUESTION 5.
Distinguish between strong and weak acid. Give an example of each.
ANSWER
Strong acid is the one which ionizes fully producing more hydrogen ions when in solution with water e.g.
- Hydrochloric acid
- Nitric acid
- Sulphuric acid
A weak acid is the one which ionizes partially in a solution of water producing few hydrogen ions
e.g.
- Ethanoic acid
- Propanoic acid
QUESTION 6.
Describe how a solid sample of Lead (II) chloride can be prepared using the following reagents. Dilute nitric acid (Nitric (V) acid), dilute Hydrochloric acid and lead (II) carbonate.
ANSWER
Add excess Lead (II) Carbonate to Nitric acid. Wait for the reaction to be completed. Filter the resulting solution mixture. To the filtrate (Lead Nitrate) add excess dilute hydrochloric acid. Filter the mixture to get lead (II) chloride. PbCO3(s) + 2HNO3(aq) →Pb(NO3)2(aq) + H2O(l) + CO2(g) Pb(NO3)2(aq) + 2HCl(aq) →PbCl2(s) + 2HNO3(aq)
QUESTION 7.
A beekeeper found that when stung by a bee, the application of a little solution of sodium hydrogen Carbonate help to relieve the irritation from the affected area. Explain.
ANSWER
The sting from the bee contains Histamine which is acidic. This causes irritation. Sodium hydrogen carbonate is alkaline/ basic and neutralizes the acid to remove the irritation.
QUESTION 8.
State and explain the observations that would be made when a few drops of concentrated sulphuric acid are added to a small sample of hydrated copper (II) sulphate.
ANSWER
The blue crystal changed to a white powder. Conc sulphuric acid is a dehydrating agent. It removes water of crystallization from hydrated copper (II) sulphate. CuSO4:5H2O Conc H2SO4 + CUSO4 +5H2O(l) Blue crystals White powder.
QUESTION 9.
(A) A few drops of freshly prepared iron (II) sulphate solution were added to potassium Nitrate solution in a test tube. Concentrated sulphuric acid was then carefully added to the mixture. State the observation that was made.
(B) Write an equation for the reaction that occurs when solid potassium nitrate is strongly heated.
ANSWER
(A) Brown ring where the layers of acid meet the layer of the nitrate and sulphate.
(B) 2KNO3(s) => heat => 2KNO2(aq) + O2 (g)
QUESTION 10.
The PH of a sample of soil was found to be 5.0. An agricultural officer recommended the addition of calcium oxide in the soil. State two functions of calcium oxide in the soil.
ANSWER
To neutralize soil acidity
- Add Ca2+ ions to the soil which is needed by plants i.e. it acts as a fertilizer.
QUESTION 11.
In the experiment, 30cm3 of 0.1M sulphuric acid was reacted with 30cm3 of 0.1M sodium Hydroxide.
a) Write an equation for the reaction that took place (1mk)
b) State the observations that were made when both blue and red litmus papers were dropped into the mixture. (1mk)
c) Give a reason for your answer in (b) above.
ANSWER
(a) H2SO4(aq) + 2NaOH(aq) → Na2SO4(aq) + H2O(l)
(b) Blue litmus paper changed to red. The red litmus remained red.
(c) The acid used was in excess i.e
Moles of both acid and bases are 30 x 0.1 = 0.003 moles
1000
But NaOH: H2SO4 reacts in the ratio of 2:1
Hence we expect 0.003 moles of NaOH to react with 0.0015 moles of H2SO4.
The acid was in excess by 0.0015 moles.
QUESTION 12.
In an experiment, equal amounts of magnesium powder were added into test tubes 1 and 2 as shown below.
ANSWER
Hydrochloric acid is a strong acid. It ionizes fully in a solution of water.
Therefore there are more hydrogen ions to be displaced by magnesium. Ethanoic acid is a weak acid. It ionizes partially in a solution of water. It contains few hydrogen ions to be displaced by magnesium.
QUESTION 13.
Ammonia gas was passed into the water as shown below
(a) When a red litmus paper was dropped into the resulting solution, it turned blue. Give a reason for this observation.
(b) What is the function of the funnel?
ANSWER
a) Ammonia gas reacts with water producing ammonia solution NH3(g) + H2O(l) →NH4OH(aq) Ammonia solution is a weak alkali. It ionizes partially producing hydroxyl ions [OH- ].
The [oh- ] ions change red litmus to blue.
(b) The funnel prevents the sucking back of water as ammonia is very soluble in water.
NOTE: Questions are updated daily, so keep on coming for more knowledge. Thank you.