In a laboratory preparation of hydrogen gas, what would happen (write chemical reactions) if the following changes are made?
1) in place of zinc granules, same amount of zinc dust is taken in test tube
2) instead of dilute sulphuric acid, hydrochloric acid is taken
3) In place of zinc, copper turning are taken
4) sodium hydroxide is taken in place of sulphuric acid and tube is heated
1) in place of zinc granules, same amount of zinc dust is taken in test tube
2) instead of dilute sulphuric acid, hydrochloric acid is taken
3) In place of zinc, copper turning are taken
4) sodium hydroxide is taken in place of sulphuric acid and tube is heated
(a) When zinc dust is taken instead of zinc granules to react with sulphuric acid, the hydrogen gas is formed. But the rate of reaction increases in the case of zinc dust compared to the zinc granules, because of increase in surface area there is increases the rate of reaction.
Thus, when zinc dust is used in the place of zinc granules, hydrogen gas is produced at a faster rate.
(b) Zinc granules give hydrogen gas; along with zinc chloride; when they react with hydrochloric acid.
Thus, when hydrochloric acid is used at the place of sulphuric acid, zinc chloride is formed in place of zinc sulphate; along with hydrogen gas and reaction takes place at the same rate.
(c) Zinc reacts with dilute nitric acid to form zinc nitrate and hydrogen gas.
Zn(s) + 2HNO3(aq) —> Zn(NO3)2(aq) + H2(g)
(d) Copper does not react with dilute acids in normal condition because copper lies at lower position in reactivity series and is considered as a noble metal.
Thus, if copper turning is taken in place of zinc granules, no reaction will take place.
(e) If sodium hydroxide is taken in place of dilute sulphuric acid and the tube is heated, sodium zincate is formed along with hydrogen gas. But heating of test tube will increase the rate of formation of hydrogen gas as heating of reaction mixture increases the rate of reaction.
Zn + 2NaOH --------------> Na2ZnO2 + H2
Sodium zincate
(a) When zinc dust is taken instead of zinc granules to react with sulphuric acid, the hydrogen gas is formed. But the rate of reaction increases in the case of zinc dust compared to the zinc granules, because of increase in surface area there is increases the rate of reaction.
Thus, when zinc dust is used in the place of zinc granules, hydrogen gas is produced at a faster rate.
(b) Zinc granules give hydrogen gas; along with zinc chloride; when they react with hydrochloric acid.
Thus, when hydrochloric acid is used at the place of sulphuric acid, zinc chloride is formed in place of zinc sulphate; along with hydrogen gas and reaction takes place at the same rate.
(c) Zinc reacts with dilute nitric acid to form zinc nitrate and hydrogen gas.
Zn(s) + 2HNO3(aq) —> Zn(NO3)2(aq) + H2(g)
(d) Copper does not react with dilute acids in normal condition because copper lies at lower position in reactivity series and is considered as a noble metal.
Thus, if copper turning is taken in place of zinc granules, no reaction will take place.
(e) If sodium hydroxide is taken in place of dilute sulphuric acid and the tube is heated, sodium zincate is formed along with hydrogen gas. But heating of test tube will increase the rate of formation of hydrogen gas as heating of reaction mixture increases the rate of reaction.
Zn + 2NaOH --------------> Na2ZnO2 + H2
Sodium zincate
