Question

There is about 1.0 g of calcium, as Ca²+, in 1.0 L of milk. What is the molarity of Ca²+ in milk?

a) 0.025 M
b) 0.050 M
c) 0.075 M
d) 0.100 M

Answer 1

The molarity of Ca²⁺ in milk is calculated using the mass of calcium and its molar mass, resulting in approximately 0.025 M, which corresponds to option (a).

Step-by-step explanation:

To calculate the molarity of Ca²⁺ in milk, we start by finding the number of moles of calcium. We use the molar mass of calcium (about 40.08 g/mol) to convert the mass of calcium to moles:

moles of Ca²⁺ = mass of Ca²⁺ / molar mass of Ca

moles of Ca²⁺ = 1.0 g / 40.08 g/mol = 0.02495 moles

Molarity (M) is defined as the number of moles of a solute per liter of solution. Since we have approximately 0.02495 moles of Ca²⁺ in 1.0 L of milk, the molarity is approximately 0.02495 M, which can be rounded to 0.025 M.

Therefore, the correct option is (a) 0.025 M.