Question

How many moles of solute are contained in 200 millilitres of a 1 M solution?

Answer 1

Here, we have given the molarity of a certain solution which is in fact the concentration of that solution. Also, volume of the same solution is also mentioned; which signifies the easiest way to solve this problem.

Complete step-by-step answer: Let us solve this step by step by considering some key points as well;
Molarity-
It is one of the forms of concentration described i.e. molarity is the moles of solute per litre of solution. It is denoted by M and has units as mol/L.
$Molarity=\dfrac{moles\left( solute \right)}{volume\left( solution \right)}$
So,
In this given statement we need to find the number of moles of solute when we have given molarity i.s. concentration of solution and the volume of solution. Thus,
$M=\dfrac{n}{V} \\\ \Rightarrow n=M\times V \\\ \Rightarrow n=1M\times 200ml=1mol{{L}^{-1}}\times 200\times {{10}^{-3}}L \\\ \Rightarrow n=0.2mol \\\$

Note: Do note that the units are consistent here, so the unit “L” will get cancelled and we will result in “mol” easily; still care must be taken while resolving millilitres into litres.