Question

You explored the relationship between molarity, the number of moles, and solution volume. However, when you prepare a solution, you are unable to directly measure the number of moles of solute. Instead, you can mass the solute and convert between the number of moles and mass using the molar mass of a substance as a conversion factor. The molar mass of a substance can be calculated based on its molecular formula; otherwise, it can be calculated from the mass and number of moles as follows: Molar Mass = Mass solute (in g)Moles solute In order to prepare a certain volume of solution with a desired concentration, you would need to determine the required mass of solute. What mass of CaCl2 would you need to prepare a 100. mL solution at a concentration of 0.240 M ? Express the mass in grams to three significant figures.

Answer 1

Answer:

2.64gram

Explanation:

Molarity, which refers to the molar concentration, is calculated thus:

Molarity = number of moles (n) ÷ volume (L)

According to the question, volume = 100 mL, molarity = 0.240 M.

Since 1L = 1000mL

100 mL = 100/1000

= 0.1L

Hence;

0.240 = n/0.1

n = 0.1 × 0.240

n = 0.024mol

Mole = mass/molar mass

Molar mass of CaCl2 = 40 + 35.5(2)

= 40 + 71

= 111g/mol

mass = molar mass × mole

mass = 110 × 0.024

Mass = 2.64gram