Question

What mass of Noah (M=40g/mol) should be dissolved in 125ml water to form a 0.65M solution

Answer 1

Answer:

M = mass * 1000/Molecular mass * vol(ml)

0.65 = mass of NaOH * 1000 / 40 * 125

mass of NaOH = 0.65 * 40 * 125 / 1000

                         = 3.25 gm

Thus , mass of NaOH required is 3.25 gm.

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Answer 2

Answer:

Given:

Gram Molecular Mass NaOH = 40 g/mol

Dissolved in (V)in ml = 125 ml

Molarity (M) = 0.65 M

To Find:

Mass of NaOH to be dissolved in 125 ml water to get a 0.65M solution

Solution:

We know that,

Molarity (M) is given by the formula,

$\blue{\boxed{\rm M = \dfrac{W}{GMW} \times \dfrac{1000}{V(in \;ml)}}}$

Where,

M = Molarity

W = Weight of NaOH to be dissolved

GMW = Gram Molecular Weight

Given that,

M = 0.65 M

GMW = 40 g/mol

V(in ml) = 125 ml

Here,

We are asked to find Weight of NaOH to be dissolved (W)

Hence, by substituting the above values in the given formula

We get,

$\green{\rm \implies 0.65= \dfrac{W}{40} \times \dfrac{1000}{125}}$

$\orange{\implies \rm W=\dfrac{0.65 \times 40 \times 125}{1000}\;g}$

$\rm \implies W = \dfrac{3250}{1000}\;g$

$\pink{\rm \implies W = 3.25\;g}$

$\red{\boxed{\boxed{\rm W = 3.25\;g}}}$

Hence,

Weight of NaOH to be dissolved in 125ml water to form a 0.65M solution is 3.25 g