Question

sample	CaCl2, M	Moles of Ca2+ in 20 mL of solution	Theoretical amount of CaCO3 precipitate	Volume of .5M Na2CO3 (20% excess)	Theortical water hardness, mg/mL
1	.400
2	.200
3	.500
4	.100
5	.050
6	.300

Each sample has been concentrated by a factor of 100

complete table

Answer 1

sample	CaCl2, M	Moles of Ca2+ in 20 mL of solution	Theoretical amount of CaCO3 precipitate	Volume of .5M Na2CO3 (20% excess)	Theortical water hardness, mg/mL
1	.400*100 = 40	(20 mL/1000 mL)*40 M = 0.8 mol	0.8 mol*100 g/mol = 80 g	0.8*(120/100) mol/0.5 M = 1.92 L	80 g/20 mL = 4 g/mL = 4000 mg/mL
2	.200*100 = 20	(20 mL/1000 mL)*20 M = 0.4 mol	0.4 mol*100 g/mol = 40 g	0.4*(120/100) mol/0.5 M = 0.96 L	40 g/20 mL = 2 g/mL = 2000 mg/mL
3	.500*100 = 50
4	.100*100 = 10
5	.050*100 = 5
6	.300*100 = 30

Similarly, you can complete the 3^rd, 4^th, 5^th and 6^th rows.

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