Question

What mass of KBr is present in 25 mL of a 0.85 M solution of potassium chloride?

Answer 1

Answer : The correct answer for mass of KBr = 2.53 g

Given :

Molarity of KBr solution = 0.85 M

Volume of KBr solution = 25 mL

Converting volume from mL to L ( 1 L = 1000 mL )

`Volume of solution = 25 mL * (1 L )/(1000mL)`

Volume of solution = 0.025 L

Mass of KBr = ?

Mass of KBr can be calculated using following steps :

1) To find mole of Kbr :

Mole of KBr can be calculated using molarity .

Molarity : It is defined as mole of solute present in volume of solution in Liter .

It uses unit as M or
`(mol)/(L)`

It can be expressed as :

`Molarity = (mol of solute (mol))/(volume of solution (L))`

Plugging value of molarity and volume

`0.85 (mol)/(L) = (mol of Kbr)/(0.025 L)`

Multiplying both side by 0.025 L

`0.85 (mol)/(L) * 0.025 L = (mole of KBr)/(0.025 L) * 0.025 L`

Mole of KBr = 0.02125

2) To find mass of Kbr :

Mass of Kbr can be calculated using mole . Mole can be expressed as :

`Mole (mol) = (mass (g) )/(molar mass (g)/(mol) )`

Mole of Kbr = 0.02125 mol

Molar mass of KBr = 119.00
`(g)/(mol)`

Plugging values in mole formula

`0.02125 mol = (mass (g))/(119.00 (g)/(mol))`

Multiplying both side by 119.00
`(g)/(mol)`

`0.02125 mol * 119.00 (g)/(mol) = (mass (g))/(119.00 (g)/(mol)) * 119.00(g)/(mol)`

Mass of KBr = 2.53 g