Question 1
The concentration of K⁺ ions in 100 mL of 0.0500 M
K₂CO₃ solution, in g L^-1, is

A. 0.196
B. 0.391
C. 1.96
D. 3.91

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Question 2
Carbon monoxide can be oxidised to carbon dioxide.
2CO(g) + O₂(g) → 2CO₂(g)
3 mol of CO and 2 mol of O₂ are mixed.
When the reaction is complete there will be
A. 4 mol of CO₂ produced.
B. 2 mol of CO₂ produced.
C. 1 mol of CO unreacted.
D. 0.5 mol of O₂ unreacted.

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A soluble fertiliser contains phosphorus in the form of phosphate ions (PO₄^3-). To determine the PO₄^3- content
by gravimetric analysis, 5.97 g of the fertiliser powder was completely dissolved in water to make a volume
of 250.0 mL. A 20.00 mL volume of this solution was pipetted into a conical flask and the PO₄^3- ions in the
solution were precipitated as MgNH₄PO₄. The precipitate was filtered, washed with water and then converted
by heating into Mg₂P₂O₇. The mass of Mg₂P₂O₇ was 0.0352 g.

a. Calculate the amount, in mole, of Mg₂P₂O₇.

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b. Calculate the amount, in mole, of phosphorus in the 20.00 mL volume of solution.

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c. Calculate the amount, in mole, of phosphorus in 5.97 g of fertiliser.

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d. Calculate the percentage of phosphate ions (PO₄^3-) by mass in the fertiliser. Ensure you express your answer to an appropriate number of significant cant figures.

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