Question

7. How many grams of sodium chloride are in 250 mL of a 2.5M NaCl solution?

Answer 1

Given, volume of solution is 250ml or 0.25 liter.
Molarity of NaCl = 0.50M
Now, according to molarity formula
M = n/V(in L)
where , n = no. of mole of solute(NaCl)
put the value
0.5 = n/0.25
=> n = 0.5×0.25
=> n = 0.125mole
So, number of mole of solute (NaCl) is 0.125mole present in solution .
Now , molecular mass of NaCl is
NaCl = 23+ 35.5 = 58.5
Now, according to formula
number if mole = mass of NaCl/molecular mass
=> 0.125 = mass of NaCl/58.5
=> mass of NaCl = 0.125×58.5 = 7.3125g
Hence, 7.3125 grams of sodium chloride is present in 250mL.