Which of the following combination will produce H2 gas?
A
Au metal and NaCN(aq) in the presence of air
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B
Cu metal and conc.HNO3
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C
Fe metal and conc.HNO3
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D
Zn metal and NaOH(aq)
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Solution
The correct option is DZn metal and NaOH(aq) Zn metal and NaOH(aq) will produce hydrogen gas. Zn+2NaOH→Na2ZnO2+H2↑ Gold react with sodium cyanide, oxygen and water, but no hydrogen gas is obtained. 4Au+8NaCN+O2+2H2O→4Na[Au(CN)2]+4NaOH Cu metal reacts with conc. nitric acid but no hydrgen gas is obtained. Cu+4HNO3→Cu(NO3)2+2H2O+2NO2↑ Fe metal reacts with conc. nitric acid but no hydrgen gas is obtained. Fe+6HNO3→Fe(NO3)3+3H2O+3NO2↑