Question

Sodium phosphate and calcium chloride react to form sodium chloride and calcium phosphate. If you have 379.4 grams of calcium chloride and an excess of sodium phosphate, how much calcium phosphate can you make? Use the periodic table and the polyatomic ion resource.
A. 353.5 g
B. 379.4 g
C. 402.2 g
D. 863.4 g
E. 1,060 g

Answer 1

Answer:- A. 353.5 g

Solution:- The balanced equation is:

$2Na_3PO_4(aq)+3CaCl_2(aq)\rightarrow 6NaCl(aq)+Ca_3(PO_4)_2(s)$

From this equation, there is 3:1 mol ratio between calcium chloride and calcium phosphate.

Grams of calcium chloride are converted to moles and these moles are multiplied by the mol ratio to get the moles of calcium phosphate. Finally the moles are multiplied by molar mass to get the grams of calcium phosphate.

Molar mass of $CaCl_2$ = 40.078+2(35.45) = 110.978 g per mol

Molar mass of $Ca_3(PO_4)_2$ = 3(40.078)+2(30.974)+8(16.00)

= 120.234+61.948+128.00 = 310.182 g per mol

let's make the set up using dimensional analysis.

$379.4gCaCl_2(\frac{1molCaCl_2}{110.978gCaCl_2})(\frac{1molCa_3(PO_4)_2}{3molCaCl_2})(\frac{310.182gCa_3(PO_4)_2}{1molCa_3(PO_4)_2})$

= $353.5gCa_3(PO_4)_2$

Hence, 353.5 g of calcium phosphate will form and so the correct option is A.