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I am writing a lab report for the preparation of sodium sulfate crystals. This question came up: Why can the reaction between a metal and an acid not be used to make sodium salts?
In this case, could one not use sodium metal and sulfuric acid to make sodium sulfate, as in the following:
$$\ce{2Na + H2SO4 -> H2 + Na2SO4}?$$
Normally, reacting a metal and an aqueous acid will produce a salt and hydrogen gas, as in the case of iron:
$$\ce{Fe (s) + 2HCl(aq) -> FeCl2 (aq) + H2 (g)}$$
However, you should not use the same method to produce, for example, sodium chloride:
$$\ce{2Na (s) + 2HCl(aq) -> 2NaCl (aq) + H2 (g)}$$
because sodium reacts violently with water.
Sodium reacts vigorously with water to form sodium hydroxide and hydrogen gas:
$$\ce{Na(s) + H2O (l) -> NaOH (aq) + 1/2 H2(g)}$$
So, it is advised not to put it into water as explosions can occur. It's also highly unlikely to obtain pure salt solution. So, these salts are mostly made by mixing an acid and an alkali.
