Mutliply the mole of aluminium nitrate units by the ratio to get tot he number of mole of sodium chloride units
3 X 4 = 12 mole of NaCl
Multiply the mole of NaCl by its formula mass (58.5 atomic mass units)
12 X 58.5 =702 grams
No
you must calculate the mass of sodium chloride
NOT the number of units.
You must start with the number of aluminium nitrate units. You are given 2.4 X
units of aluminium nitrate.
No
You can not start with mass you are
given 2.4 X units of aluminium nitrate.
Divide the number of aluminium nitrate units
by avogadros number.
The mole of aluminium nitrate is 4.
Stoichiometry exercise Number to mass 

Aluminium nitrate is mixed with sodium chloride according to the equation on the right. What mass of sodium chloride must react with units of aluminium nitrate? Do you need help? If Yes click once on the equation on the right to display the help diagram. Click twice to hide the help diagram. Click on the squares in the help diagram for more information. 
Na = 23, Cl=35.5, N =14, O =16, Al =27 