5(i)
Calcium oxide is a drying agent which removes water vapour. A student wanted to collect a dry sample of the hydrogen chloride gas produced. The student set up the apparatus as shown below but was unsuccessful in collecting any gas.
(a) What mistake did the student make?
(b) What change should be made by the student in order to collect the dry HCl gas?
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(a) The student was unsuccessful in collecting any gas because calcium oxide (quick lime) react with hydrogen chloride.
CaO + 2HCl ⟶ CaCl2 + H2O
(b) The student can use conc. sulphuric acid as a drying agent. Conc. H2SO4 absorbs water vapour but does not react with HCl gas.