How many moles of calcium chloride are needed to react completely with 6.2 moles of silver nitrate

3.1 mol

Step-by-step explanation:

The balanced equation is

CaCl₂ + 2AgNO₃ ⟶ Ca(NO₃)₂ + 2AgCl

You want to convert moles of AgNO₃ to moles of CaCl₂.

The molar ratio is 2 mol AgNO₃:1 mol CaCl₂

Moles of CaCl₂ = 6.2 mol AgNO₃ × (1 mol CaCl₂/2 mol AgNO₃)

Moles of CaCl₂ = 3.1 mol CaCl₂

The reaction will require 3.1 mol of CaCl₂.

the formula mass of a molecule or a compound is the sum of the atomic weights of the atoms in its empirical formula

(that's what i know about formula mass)