Question

Q6(a) What is molality .5 gm of NaOH is dissolved in250 gm water Find the molality .​

Answer 1

Explanation:

Hence, the correct answer is 6.25

Answer 2

$\underline{\textsf{\textbf{\purple{ \mapsto Given:}}}}$

• 5g of NaOH is dissolved in water.
• The Volume of water is 250gm.

$\underline{\textsf{\textbf{\purple{ \mapsto To\:Find:}}}}$

• The molality of the solution

$\underline{\textsf{\textbf{\purple{ \mapsto Concept\:Used:}}}}$

We know that Molality is defined as , Number of moles of solute present per kilogram of solvent that is Molality = n(moles of solute)/ Mass of solvent ( in kg ) .

$\underline{\textsf{\textbf{\purple{ \mapsto Answer:}}}}$

Here we know that molar mass of NaOH = 23g + 16g + 1 = 40g .

Given mass of NaOH is 5g .

So we know number of moles as

➥ n(moles) = Given weight / Molecular weight.

➥ n(moles) = 5g/40g.

➥ n(moles) = 1/8.

Now here solvent is water and its weight is 250g = 250/1000kg = 1/4 kg .

Hence we know ,

$\boxed{\red{\tt \dashrightarrow Molality=\dfrac{n(moles \;of\:solute}{Mass\:of\:solvent(in\:kg)}}}$

➥ m = n(moles)/Mass of solvent (in kg ).

➥ m = 1/8 mol ÷ 1/4 kg

➥ m = 1/8 × 4 mol/kg.

➥ m = 1/2 = 0.5 mol/kg .

Hence the Molality is 0.5m .