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# Can someone help me solve 3 molarity (chemistry) questions?

I have 3 questions, 2 of which I think I know, and 1 that I do not. Please help me do the 1 and check my other 2 to see if they are correct. Fastest and clearest answer = automatic best!

1. You dissolve 12.47g of MgCl2 in wate to make 150 mL of solution. What is the molarity of chloride ion?

2. 25 mL of 0.500M NaCl is mixed with 35 mL of 0.350M CaCl2. What is the molarity of the chloride ion in the solution?

My answer: 0.4125M

3. Density of copper sulfate solution CuSO4 is 1.184g/mL. What is the molarity of this solution that contains 35g CuSO4 / 100g of solution?

My answer: 7.4M

### 2 Answers

- Anonymous1 decade agoFavorite Answer
1) 12.47 g MgCl2 * [(1 mole MgCl2)/(95.21g MgCl2)] * [(2 moles Cl)/(1 mole MgCl2)

=.2619 moles Cl

.2619 moles Cl / .150 L sol'n = 1.75 M

- Anonymous1 decade ago
1.

MgCl2 -> Mg+ + 2Cl-

n=m/M

= 12.47 / 95

= 0.13126 mol of MgCl2 so double for Cl- because of equation

0.13126 x 2

=0.26252 mol Cl-

2.

I got:

25ml = 0.025dm3

(0.500 / 1000) x 25

= 0.0125mol

35ml = 0.035dm3

(0.350 / 1000) x 35

=0.01225 x 2 (because of 2 lots of Cl- for every CaCl2)

= 0.0245mol

Total = 0.0125 + 0.0245

= 0.0370mol Cl-

I'm not to clear on the third so I'll have another look later and see if anyone else has any better solutions.