M = Sr (strontium)
Step 1. Calculate the moles of CO_2.
Moles of CO_2 = 0.395 g CO_2 × (1 mol CO_2/44.01 g CO_2)
= 0.008 975 mol CO_2
Step 2. Calculate the moles of MCO_3.
Moles of MCO_3 = 0.008 975 mol CO_2 × (1 mol MCO_3/1 mol CO_2)
= 0.008 975 mol MCO_3
Step 3. Calculate the molar mass of MCO_3
MM = grams/moles = 1.324 g/0.008 75 mol = 147.5 g/mol
Step 4. Calculate the atomic mass of M
M_r = x + 12.01 + 3×16.00 = x + 60.01 = 147.5
x = 147.5 – 60.01 = 87.5
Step 5. Identify M.
The element with the closest atomic mass is Sr (A_r = 87.6).
∴ M = Sr and the compound is SrCO_3.
