I'd say b, but i'm not 100 percent sure.<span />
Calcium reacts gently with water to give hydrogen and calcium hydroxide, which is only slightly soluble, thus slows down the reaction.
It will be assumed that hydrochloric acid used is a dilute aqueous solution.
However, calcium reacts with hydrochloric acid to give calcium chloride which is readily soluble in water, and hydrogen, being a typical reaction of relatively active metals with acids.
Ca(s) + 2HCl(aq) -> CaCl2(aq) +H2(g) ↑ + heat
The clues that it is a chemical reaction could be:
- formation of a new substance, gaseous hydrogen
- disappearance of a metallic solid in the solution
- heat formed during the vigorous reaction.
As silver is below hydrogen in the electrochemical series, it will not be expected to react with dilute hydrocloric acid. (however, it dissolves in oxidizing acid such as nitric acid, but not displacing hydrogen as a product).
Answer:
c. H2(g) + CuO(s) → Cu(s) + H2O(l)
e. H2(g) + Cl2(g) → 2HCl(g)
Explanation:
A redox reaction is a reaction that involves a changes in oxidation number of the species involved in the reaction.
The oxidizing agent experiences a decrease in oxidation number while the reducing agent experiences an increase in oxidation number.
For H2(g) + CuO(s) → Cu(s) + H2O(l)
Copper is reduced from +2 to 0 while hydrogen is oxidized from 0 to +2 Hence hydrogen is the reducing agent while copper is the oxidizing agent.
For H2(g) + Cl2(g) → 2HCl(g)
Chlorine is reduced from 0 to -1 while hydrogen is oxidized from 0 to +1. Hence chlorine is the oxidizing agent while hydrogen is the reducing agent.
1 mole<span> H2O = 18.0 g H2O.</span>
<span>25 g H2O </span>1 mol<span> H2O.</span>
