Question

How many milliliters of calcium, with a density of 1.55 g/mL, are needed to produce 85.8 grams of calcium fluoride in the single replacement reaction below? Show all steps of your calculation as well as the final answer.

Unbalanced equation: Ca + HF “yields”/ CaF2 + H2

Answer 1

@Kainui @halorazer

Answer 2

@iPwnBunnies

Answer 3

First let's balance the reaction:

\[Ca +2HF \rightarrow CaF_{2}+H_{2}\]
We're given the amount of CaF2 we end up with, and want to use it to work backwards and find out how much Ca we started with. First thing to do is find how many moles of CaF2 we have: 85.8 g / 78 g/mol = 1.1 mol.

According to the reaction, for every mole of CaF2 produced, 1 mole of Ca is used up. If we end up with 1.1 mol of CaF2, we must have also started with 1.1 mol of Ca. We want to find how many mL of Ca were used. We can find mL from density as long as we have mass. We can find mass because we have moles. The mass of Ca used is 1.1 mol x 40 g/mol = 44 g. The volume of Ca used is therefore 44 g / 1.55 g/mL = 28.4 mL.