calculating molarity by mass?

Question

What is the molarity of a sodium chloride solution made by dissolving 263.7g to make 2.0L?




What mass CaBr2 is needed to make 500.0mL of 0.554M solution?

Answer 1

a. molarity of NaCl
M=mole/L
find number of mole
263.7g*(1mole/58.44g) = 4.51 mole
(NaCl=58.44g/mole)
M=4.51 mole/2.0L=2.25M=2.3M
b. mass
500.0mL*(1L/1000mL)*(.554mole / L) =.277mole
mass CaBr2= .277mole*199.88g / mole= 55.36g= 55.4g
good luck

Answer 2

a) NaCl= 58.5 g/mol >> 263.7g = 4.51 mol NaCl

If M=n/L ==> 4.51mol/2 L = 2.255 M

b) CaBr2 = 200g/mol >> 1L of a 0.554 M solution = 110.8 g

Then, 500 mL of the same solution = 55.4g