Question

The mass of mgcl2 should be dissolve in 750gm of water in order to prepare a 1.05m solution is

Answer 1

m =wt of solute /95 X 1000/750

1.05 =wt of solute /95 X 1000/750

wt of solute =1.05x95x750/1000=74.8gm

Answer 2

Answer:

74.1gm of $MgCl_{2}$ must be dissolved in water.

Explanation:

Given that,

Mass of water in which $MgCl_{2}$ is to be dissolved =750gm=0.75kg

Molality of Magnesium chloride solution =1.05m

We are required to find the Mass of magnesium chloride to be dissolved in the solvent.

We know that molality is the ratio of number of moles of a solute to the weight of solvent(in kg).Therefore,

$m=\frac{n}{W_{solvent}}$

Substituting the given value in above relation,we get

$1.05=\frac{n}{0.75}= > n=1.05\times0.75=0.78mol$

We know that number of moles of an compound is the ratio of its mass to the molar mass.The molar mass of $MgCl_{2}$ is 95gm.

Hence,we can write

$0.78=\frac{m}{95} = > m=95\times0.78=74.1gm$

Therefore,74.1gm of $MgCl_{2}$ must be dissolved in water.

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