Question

What mass of solute is contained in 25.4 ml of a 1.56 m potassium bromide solution?

Answer 1

Answer : The mass of solute is 4.72 grams.

Explanation :

Molarity : It is defined as the number of moles of solute present in one liter of volume of solution.

Formula used :

$\text{Molarity}=\frac{\text{Moles of solute}}{\text{Volume of solution (in L)}}$

or,

$\text{Molarity}=\frac{\text{Mass of solute}\times 1000}{\text{Molar mass of solute}\times \text{Volume of solution (in mL)}}$

In this question, the solute is potassium bromide.

Given:

Volume of solution = 25.4 mL

Molarity = 1.56 M

Molar mass of potassium bromide = 119 g/mole

Now put all the given values in this formula, we get:

$1.56M=\frac{\text{Mass of solute}\times 1000}{119g/mole\times 25.4L}$

$\text{Mass of solute}=4.72g$

Therefore, the mass of solute is 4.72 grams.

Answer 2

Answer is: mass of potassium bromide is 4.71 grams.
V(KBr) = 25.4 mL ÷ 1000 mL/L = 0.0254 L, volume of solution.
c(KBr) = 1.56 mol/L.
n(KBr) = c(KBr) · V(KBr).
n(KBr) = 1.56 mol/L  0.054 L.
n(KBr) = 0.0396 mol, amount of substance.
m(KBr) = n(KBr) · M(KBr).
m(KBr) = 0.0396 mol · 119 g/mol.
m(KBr) = 4.71 g.
M - molar mass.