What mass of cobalt(II)phosphate will precipitate when excess sodium phosphate solution is added to 100.0 mL 0.500 M cobalt(II)nitrate?
A)6.11 g
B)9.2 g
C)18.3 g
D)36.7 g
E)55.0 g

Question

Quizplus · Accepted Answer

The reaction between cobalt(II) nitrate and sodium phosphate can be represented by the balanced chemical equation: $$3Co(NO_3)_2 + 2Na_3PO_4 \rightarrow Co_3(PO_4)_2 + 6NaNO_3$$. From the equation, 3 moles of cobalt(II) nitrate react with 2 moles of sodium phosphate to produce 1 mole of cobalt(II) phosphate. Given that the solution of cobalt(II) nitrate is 0.500 M and the volume is 100.0 mL (0.100 L), the moles of cobalt(II) nitrate are $0.500 \, \text{M} \times 0.100 \, \text{L} = 0.050 \, \text{moles}$. According to the stoichiometry of the reaction, 3 moles of cobalt(II) nitrate yield 1 mole of cobalt(II) phosphate, so $0.050 \, \text{moles} \, Co(NO_3)_2 \times \frac{1 \, \text{mole} \, Co_3(PO_4)_2}{3 \, \text{moles} \, Co(NO_3)_2} = 0.0167 \, \text{moles} \, Co_3(PO_4)_2$. The molar mass of cobalt(II) phosphate, $Co_3(PO_4)_2$, is approximately 366.8 g/mol, so the mass of cobalt(II) phosphate that will precipitate is $0.0167 \, \text{moles} \times 366.8 \, \text{g/mol} = 6.11 \, \text{g}$.

What Mass of Cobalt(II)phosphate Will Precipitate When Excess Sodium Phosphate