A salt used as a dietary supplement is hydrated zinc sulfate, $\text{ZnSO}_4\cdot x\text{H}_2\text{O}$, which forms a colourless crystalline solid. Crystals of zinc sulfate can be made in a school or college laboratory by reacting dilute sulfuric acid with an appropriate zinc compound. Write the formulae of two simple zinc compounds that could each react with dilute sulfuric acid to form zinc sulfate.
A straightforward method for finding the value of $x$ in the formula $\text{ZnSO}_4\cdot x\text{H}_2\text{O}$ is to heat it carefully so that the water is removed. $\text{ZnSO}_4\cdot x\text{H}_2\text{O}(s) \rightarrow \text{ZnSO}_4(s) + x\text{H}_2\text{O}(g)$ A student put some hydrated zinc sulfate into a weighed boiling tube and then recorded its mass. The tube was heated briefly, allowed to cool, and weighed again once cool. This sequence was carried out four times. The final results are shown below. (i) Why was the boiling tube heated, cooled and reweighed four times? (ii) Calculate the amount, in moles, of the anhydrous salt formed. (iii) Calculate the amount, in moles, of water lost on heating. (iv) Use your answers to (ii) and (iii) to calculate the value of $x$ in $\text{ZnSO}_4\cdot x\text{H}_2\text{O}$.
For many people, an intake of about $15\text{ mg}$ of zinc per day is enough to avoid deficiency. Zinc ethanoate crystals, $(\text{CH}_3\text{CO}_2)_2\text{Zn}\cdot2\text{H}_2\text{O}$, may be used for this purpose. (i) What mass of pure crystalline zinc ethanoate ($M_r = 219.4$) must be taken to provide a dose of $15\text{ mg}$ of zinc? (ii) If this dose is taken as $5\text{ cm}^3$ of aqueous zinc ethanoate, what would be the concentration of the solution used? Give your answer in $\text{mol dm}^{-3}$.