Question

While making 100 ml of 2M NaCl solution, a student left the solution on a heating

platform reducing the volume by 50 ml. This solution was diluted 1:100 for use. What

is the final concentration of NaCl in this solution?
​

Answer 1

Answer:

Total volume = 500  ml  +  200  ml  =  700  ml = 0.7 L.

Number of moles of NaCl in 500 ml of 2 M solution  = 2×  

1000 ml

500 ml

​  

=1 mole.

Number of moles of NaCl in 200 ml of 2 M solution = 2×  

1000 ml

200 ml

​  

=0.4 mole.

Total number of moles of NaCl =1+0.4=1.4 moles.

Molarity of the resulting solution M=  

0.7 L

1.4 moles

​  

=2M.

Therefore, the option is A.

Explanation: