Question

What will be volume of 8 M solution containing 1 mole solute ?
(A) 150 ml
(B) 125 ml
(C) 100 ml.
(D) 175 ml.​

Answer 1

Answer:

$\boxed{(B) \: 125\: ml}$

Given:

Molarity = 8 M

No. of moles of solute = 1 mole

Explanation:

Molarity (M)

It is defined as number of moles of solute dissolved in 1 litre of solution

$\sf Molarity (M) = \frac{No.\: of \: moles\: solute}{Volume\: of\: solution\: in\: litres} \\ \\ \sf M = \frac{No.\: of \: moles\: solute \times 1000}{Volume\: of\: solution\: in\: ml}\\\\ \sf M = \frac{Weight\: solute}{Molar\: mass\: of\: solute \times Volume\: of\: solution\: in\: litres}$

So,

$\sf\implies 8=\frac{1 \times 1000}{Volume\: of\: solution\: in\: ml}\\\\ \sf \implies Volume\: of\: solution\: in\: ml \times 8=1000\\\\ \sf\implies Volume\: of\: solution\: in\: ml =\frac{1000}{8}\\\\ \sf\implies Volume\: of\: solution\: in\: ml =125\:ml$

Additional Information

Unit of molarity is $\sf \bold{mol/litre}$ or $\sf \bold{mol\: L^{-1} }$ or $\sf \bold{M(Molar)}$

Molarity of a solution depends on temperature because volume of a solution is temperature dependent.

When a concentrated solution is diluted by adding more solvent, the number of moles of solute in the solution remains unchanged.

To calculate the molarity of a solution after dilution formula used is:

$\sf \bold{M_{1}V_{1}=M_{2}V_{2}}\\\\ \sf M_{1}= Initial\: molarity\\\sf M_{2}=Molarity \: of\: new\: solution\\\sf V_{1}= Initial\: volume\\\sf V_{2}=Volume \: of\: new\: solution$

Formula of molarity for mixing two solutions of the same substance is:

$\sf \bold{M_{1}V_{1}+M_{2}V_{2}=M_{3}(V_{1}+V_{2})}\\\\ \sf M_{3}=Molarity\: of\; mixture\: formed$

Formula of molarity when $\sf \%$ strength and density is known is:

$\sf \bold{Molarity=\frac{\% \: by \: weight \times 10\times density}{Gram \: molecular \: mass} }$

Answer 2

$\huge\underline\mathtt{AnswEr:-}$

➠ Molarity = Moles/V(ml) × 1000

➠ 8 = 1/V (ml) × 1000

➠ V(ml) = 1000/8

➠ 125 ml