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Hydrogen — Chemistry STD 11 Science — Question

Gujarat BoardEnglish MediumSTD 11 ScienceChemistryHydrogen5 Marks
Question
How is dihydrogen obtained from:
  1. dilute sulphuric acid.
  2. sodium hydroxide and.
  3. water.
Explain by giving equations.
✓

Answer

  1. When metal reacts with dilute sulphuric acid, hydrogen is obtained along with metal salts.
$\text{Mg}(\text{s})+\text{H}_2\text{SO}_4(\text{aq})\xrightarrow{\ \ \ \ \ \ \ \ \ \ }\text{MgSO}_4(\text{aq})+\text{H}_2(\text{g})$
  1. When zinc reacts with sodium hydroxide, sodium zincate is formed and hydrogen gas is evolved.
$\text{Zn}(\text{s})+2\text{NaOH}(\text{aq})\xrightarrow{\ \ \ \ \ \ \ \ \ }\text{Na}_2\text{OH}_2(\text{aq})+(\text{g)}$
  1. When acidified water is electrolysed using platinum electrodes, hydrogen gas is evolved at cathode.
$\text{H}_2\text{O}\xrightarrow{\ \ \ \ \ \ }\text{H}^+(\text{aq})+\text{OH}^-(\text{aq})$
At cathode $2\text{H}^++2\text{e}^-\xrightarrow{\ \ \ \ \ \ \ \ }2\text{H}\xrightarrow{\ \ \ \ \ \ \ }\text{H}_2$
At anode $4\text{OH}^-\xrightarrow{\ \ \ \ \ \ \ }4\text{OH}+4\text{e}^-\xrightarrow{\ \ \ \ \ }2\text{H}_2\text{O}+\text{O}_2$

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