Question

What mass of barium chloride is present in a $100ml$ of barium chloride solution of $0.250mol{L^{ - 1}}$ concentration?

Answer 1

The volume of barium chloride solution is given as $100ml$ which means the volume in millilitres has to convert into litres. Substitute this volume in litres, and molar mass of barium chloride in the molarity formula and the molarity as $0.250mol{L^{ - 1}}$ to obtain the mass of barium chloride.
Formula used:
$M = \dfrac{{\dfrac{w}{m}}}{V}$
$M$ is molarity
$w$ is mass of barium chloride
$m$ is molar mass of barium chloride
$V$ is volume of solution in litres

Complete answer:
Molarity is defined as the number of moles dissolved in volume of solution in litres. The volume of solution must be in litres only, if it is in millilitres multiply the value with $1000$ . The volume of barium chloride solution is given as $100ml$ when converted into litres, the volume of solution will be $0.1L$ .
The molar mass of barium chloride will be sum of the molar mass of barium and molar mass of two chlorine atoms $137.32 + 2\left( {35.5} \right) = 208.32gmo{l^{ - 1}}$
Molarity is given as $0.250mol{L^{ - 1}}$
Substitute the values of molarity, volume of solution, and molar mass of barium chloride in the above formula.
$0.250mol{L^{ - 1}} = \dfrac{{\dfrac{w}{{208.32gmo{l^{ - 1}}}}}}{{0.1L}}$
By simplification of the above equation, the mass of barium chloride will be $w = 5.2g$
The mass of barium chloride is present in a $100ml$ of barium chloride solution of $0.250mol{L^{ - 1}}$ concentration is $5.2g$

Note:
While calculating the molarity of any substances, the volume of solution must be in litres as molarity means the number of moles dissolved in one litre of solution. The exact molar mass of barium chloride must be calculated from the molar mass of atoms based on the periodic table.