Question
$$4.28\,g$$ of $$NaOH$$ is dissolved in water and the solution is made to $$250\,cc.$$ What will be the molarity of the solution ?
A.
$$0.615\,mol\,{L^{ - 1}}$$
B.
$$0.428\,mol\,{L^{ - 1}}$$
C.
$$0.99\,mol\,{L^{ - 1}}$$
D.
$$0.301\,mol\,{L^{ - 1}}$$
Answer :
$$0.428\,mol\,{L^{ - 1}}$$
Solution :
$$\eqalign{
& {\text{No}}{\text{. of moles of}}\,\,NaOH = \frac{{4.28}}{{40}} \cr
& \,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\, = 0.107 \cr
& {\text{Volume of solution}} = 250\,c{m^3} \cr
& M = \frac{n}{{V\left( {{\text{in}}\,\,L} \right)}} \cr
& \,\,\,\,\,\,\, = \frac{{0.107}}{{250}} \times 1000 \cr
& \,\,\,\,\,\,\, = 0.428\,mol\,{L^{ - 1}} \cr} $$