This question is about magnesium, magnesium oxide and magnesium sulfate. Hydrated crystals of magnesium sulfate, $$\(\mathrm{MgSO}_{4} \cdot 7 \mathrm{H}_{2} \mathrm{O}\)$$, can be made by reacting magnesium with sulfuric acid. In an experiment, magnesium was added to $$\(30.0 \mathrm{~cm}^{3}\)$$ of $$\(0.500 \mathrm{~mol} \mathrm{dm}^{-3}\)$$ sulfuric acid. [ $$\(M_{\mathrm{r}}\)$$ value: $$\(\mathrm{MgSO}_{4} \cdot 7 \mathrm{H}_{2} \mathrm{O}=246.4 \quad A_{\mathrm{r}}\)$$ value: $$\(\mathrm{Mg}=24.3\)$$ ] (i) Calculate the number of moles of sulfuric acid used in this experiment. (1) (ii) Calculate the mass of magnesium needed to react with the sulfuric acid. (iii) Give a reason why slightly more than this mass of magnesium was used. (1) ................................................................................................................................................................................................................................................................................ ................................................................................................................................................................................................................................................................................ ................................................................................................................................................................................................................................................................................ (iv) State how the magnesium sulfate solution could be separated from the mixture produced in this experiment. (1) ................................................................................................................................................................................................................................................................................ (v) The magnesium sulfate solution was allowed to crystallise. The crystals were dried and weighed. The mass of the hydrated crystals, $$\(\mathrm{MgSO}_{4} \cdot 7 \mathrm{H}_{2} \mathrm{O}\)$$, was 2.78 g . Calculate the percentage yield in this experiment. (2)

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