Friday, 23 September 2011 @08:34
Q5 Excess zinc carbonate is added to hydrochloric acid in the preparation of zinc chloride salt.
(i) Write an ionic equation for the reaction.
Answer: ZnCO3(s) + 2HCl (aq) à ZnCl2(aq) + H20 (l) + CO2(g)
(ii) Why excess zinc carbonate is used?
Answer: Excess zinc carbonate solid can ensure that all the hydrcoholoric acid has react completely with the zinc carbonate. So only aqueous zinc chloride and water is in the solution. To make sure that hydrochloric acid has completely react with calcium carbonate to form zinc chloride.
(iii) Briefly explain how the zinc chloride crystals can be obtained.
Answer:
Step 1: Add excess zinc carbonate solid to a beaker of dilute hydrochloric acid until there is excess zinc carbonate left behind.
Step 2: Filter to remove the excess unreacted zinc carbonate solid.
Step 3: Evaporate the zinc chloride solution to remove the water and make a saturated salt solution.
Step 4: The hot saturated solution form zinc chloride crystals when it is cooled.
- Take From Chemistry Notes-