Question

How many liters of water are needed to make a 4.00 M solution using 75.0

grams of lithium bromide (LiBr)?

a) 0.22
b) 2.26
c) 226
c) .002

Answer 1

0.22L

Step-by-step explanation:

Given parameters:

Concentration of solution = 4.00M

Mass of lithium Bromide = 75g

Unknown:

Volume of water = ?

Solution:

Concentration in terms of the molarity is the number of moles of solute in a solution.

Molarity =
`(number of moles )/(volume of solution)`

let us find the number of moles first;

Number of moles =
`(mass)/(molar mass)`

Molar mass of LiBr = 7 + 80 = 78g/mol

number of moles =
`(75)/(78)`

number of moles = 0.96moles

Volume of water =
`(number of moles )/(molarity)` = 0.96/4 = 0.22L