What is the mole fraction, X, of solute and the molality, m (or b), for an aqueous solution that is 18.0% NaOH by mass?

Question 3

harina [27]

Answer: 0.118M

Explanation:

The formula for molarity is: $M=\frac{mol solute}{L solution}$

First, we need to find the number of moles of NaCl.

$2.70gNaCl*\frac{1molNaCl}{58.44gNaCl} =0.05molNaCl$

Next, we must convert millimeters to liters. We can do that by dividing the number of mL by 1000.

$\frac{425mL}{1000} =0.425L$

Now we have our needed data! All we need to do now is plug in our data to the molarity formula.

$M=\frac{0.05mol}{0.425L} =0.118M$

I hope this helps! Pls mark brainliest!! :)

4 0

2 years ago

How would you prepare 250 mL of a 0.100 M solution of fluoride ions<br> from solid CaF2?

andrey2020 [161]

In 250 mL of volumetric flask add 0.975875 grams of $CaF_2$ and dissolve it in the 250 mL of water.

Given:

The solid of calcium fluoride.

To prepare:

The 250 mL solution of 0.100 M of fluoride ions from solid calcium fluoride.

Method:

Molarity of the fluoride ion solution needed = M = 0.100 M

The volume of the fluoride ion solution needed = V = 250 mL

$1 mL = 0.001L\\V=250 mL=250\times 0.001 L=0.250 L$

The moles of fluoride ion needed = n

According to the definition of molarity:

$M=\frac{n}{V}\\0.100M=\frac{n}{0.250 L}\\n=0.100M\times 0.250 L=0.025 mol$

Moles of fluoride ion = 0.025 mol

We know that solid calcium fluoride dissolves in water to give calcium ions and fluoride ions.

$CaF_2(s)\rightarrow Ca^{2+}(aq)+2F^-(aq)$

According to reaction, 2 moles of fluoride ions are obtained from 1 mole of calcium fluoride, then 0.025 moles of fluoride ions will be obtained from:

$=\frac{1}{2}\times 0.025 mol=0.0125 \text{mol of } CaF_2$

Moles of calcium fluoride = 0.0125 mol

Mass of calcium fluoride needed to prepare the solution :

$=0.0125 mol\times 78.07 g/mol=0.975875 g$

Preparation:

Weight 0.975875 grams of calcium fluoride
Add weighed calcium fluoride to a volumetric flask of the labeled volume of 250 mL.
Now add a small amount of water to dissolve the calcium fluoride completely.
After this add more water up to the mark of the volumetric flask of volume 250 mL.