Question

A chemist prepares a solution of calcium bromide CaBr2 by measuring out 188.μmol of calcium bromide into a 450.mL volumetric flask and filling the flask to the mark with water.

Calculate the concentration in /molL of the chemist's calcium bromide solution. Be sure your answer has the correct number of significant digits.

Answer 1

answer : 0.00042 mol/L

steps:

Concentration = moles ÷ liters

Concentration = (number of moles) / (volume in L)

Concentration = 0.000188 mol / 0.450 L = 0.000417 mol/L

The concentration of the calcium bromide solution is 0.00042 mol/L (rounded to 3 significant figures).

The first step is to calculate the number of moles of calcium bromide in the solution:

Number of moles = (mass of CaBr2) / (molar mass of CaBr2)

The molar mass of CaBr2 is:

1 x atomic mass of Ca + 2 x atomic mass of Br = 1 x 40.08 g/mol + 2 x 79.90 g/mol = 199.88 g/mol

The mass of CaBr2 is given as 188.μmol, which is equivalent to 188 x 10^-6 mol.

Therefore, the number of moles of CaBr2 in the solution is:

Number of moles = (188 x 10^-6 mol) / (1 mol/ 1000 μmol) = 0.000188 mol

The volume of the solution is given as 450 mL, which is equivalent to 0.450 L.

Therefore, the concentration of the solution is:

Concentration = (number of moles) / (volume in L)

Concentration = 0.000188 mol / 0.450 L = 0.000417 mol/L

The concentration of the calcium bromide solution is 0.00042 mol/L (rounded to 3 significant figures).

ChatGPT