Question

A solution of 10 M NaOH was used to prepare 2 L of 0.5 M NaOH. How many mL of the original NaOH solution are needed?

• A. 10 mL
• B. 100 ML
• C. 1000 ML
• D. 200 ML
• E. 2000 ML

Answer 1

The correct option is B 100 ML

No. of moles of $NaOH$ are same in both cases, so

$M_1{V}_1$$=$$M_2{V}_2$

or $V_1$$=$$M_2{V}_2/M_1$

So, $V_1$$=$$2\times .5/10$$=$$0.1L$$=$$100mL$