Question

Which of the following should be done in order to prepare a 0.4 M NaCl solution, starting with 100ml of 0.3 M NaCl solution. (M.wt of NaCl =58.5)

• A. add $5.85g$ $NaCl$
• B. add $20ml$ of water
• C. add $0.01$ moles $NaCl$
• D. evoperate $10ml$ of water

Answer 1

Answer: (A), (C)

The correct options are
A add $5.85g$ $NaCl$
C add $0.01$ moles $NaCl$

We are to prepare $0\cdot 4M$ NaCl solution and we are starting with 100 ml, $0\cdot 3M$ NaCl solution. So, we only need the moles corresponding to the difference in molarity of the two solutions.

Required moles $=(0.4-0.3)\times 0.1=0.01$