The student obtains a pure, dry sample of zinc sulfate crystals.The formula of zinc sulfate crystals is ZnSO4 .7H2 O(i) Calculate the relative molecular mass (Mr ) of zinc sulfate crystals. (2) Mr = ..............................................................(ii) The student uses 0.0200 mol of dilute sulfuric acid in her preparation.Show that the maximum mass of zinc sulfate crystals that the student could obtain is about 6 g. (2)(iii) The student obtains a mass of 4.28 g of zinc sulfate crystals.Calculate the percentage yield of the zinc sulfate crystals.Give your answer to three significant figures.
Question
The student obtains a pure, dry sample of zinc sulfate crystals.The formula of zinc sulfate crystals is ZnSO4 .7H2 O(i) Calculate the relative molecular mass (Mr ) of zinc sulfate crystals. (2) Mr = ..............................................................(ii) The student uses 0.0200 mol of dilute sulfuric acid in her preparation.Show that the maximum mass of zinc sulfate crystals that the student could obtain is about 6 g. (2)(iii) The student obtains a mass of 4.28 g of zinc sulfate crystals.Calculate the percentage yield of the zinc sulfate crystals.Give your answer to three significant figures.
Solution
(i) To calculate the relative molecular mass (Mr) of zinc sulfate crystals (ZnSO4.7H2O), you need to add up the relative atomic masses of all the atoms in the formula.
The relative atomic masses are: Zn = 65, S = 32, O = 16, H = 1
So, the Mr of ZnSO4.7H2O = (1x65) + (1x32) + (4x16) + (7x(2x1+16)) = 65 + 32 + 64 + 126 = 287
(ii) The molar mass of ZnSO4.7H2O is 287 g/mol. If the student uses 0.0200 mol of dilute sulfuric acid, the maximum mass of zinc sulfate crystals that could be obtained is (0.0200 mol) x (287 g/mol) = 5.74 g, which is approximately 6 g.
(iii) The percentage yield of the zinc sulfate crystals can be calculated using the formula:
Percentage yield = (actual yield / theoretical yield) x 100%
Here, the actual yield is 4.28 g and the theoretical yield is 5.74 g.
So, the percentage yield = (4.28 / 5.74) x 100% = 74.6% to three significant figures.
Similar Questions
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