![]() (2) What is the relationship between what you know and what you need to find out? Volume of solution used in experiment = V f = 20.00 mL Initial volume of solution = V i = 250.0 mL Mass of fertiliser = m(fertiliser) = 5.17 g (1) What information (data) have you been given in the question? Step 5: Calculate the percentage by mass of calcium in the original sample:Ĭalculate the percentage by mass of phosphate in the fertiliser. Step 4: Calculate the mass of calcium in grams (Note: 3 significant figures are justified)įrom the balanced chemical equation, the mole ratio of Ca 2+ : CaC 2O 4(s) is 1 : 1 Step 2: Calculate the moles of calcium oxalate precipitated. Step 1: Write the balanced chemical equation for the precipitation reaction:Ĭa 2+ (aq) + C 2O 4 2- (aq) → CaC 2O 4(s) The precipitate was filtered, dried and weighed to a constant mass of 2.43 g.ĭetermine the percentage by mass of calcium in the limestone sample. Question: A 2.00 g sample of limestone was dissolved in hydrochloric acid and all the calcium present in the sample was converted to Ca 2+ (aq).Įxcess ammonium oxalate solution, (NH 4) 2C 2O 4(aq), was added to the solution to precipitate the calcium ions as calcium oxalate, CaC 2O 4(s).
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