Question

Calculate the number of moles of 25g of limestone (caco3) used in a chemical reaction? (Ca=40 c=12 o=16)
2 calculate the mass of calcium chloride that can be obtained from 25g of limestone in the presence of excess hydrogen chloridw

Answer 1

1. mols CaCO3 = grams CaCO3/molar mass CaCO3
Answer is about 25/100 = about 0.025.

2. CaCO3 + 2HCl ==> CaCl2 + H2O + CO2
mols CaCO3 = 0.025
Using the coefficients in the balanced equation, convert mols CaCO3 to mols CaCl2. That will be 0.025 mol CaCO3 x (1 mol CaCl2/1 mol CaCO3) = 0.025 mols CaCl2 formed.
Now convert mols CaCl2 to grams. g CaCl2 = mols CaCl2 x molar mass CaCl2 = ?
Post your work if you get stuck.
Note: I have written the equation to show the use of HCl(aq) and not hydrogen chloride gas. I doubt the reaction will occur to a large extent with the gas but it will go 100% using aqueous HCl. Probably that is the point of the problem anyway; i.e., to use the aqueous HCl.