How many molecules are there in 2.3 grams of #NH_4SO_2#?
First calculate the molar mass of NH4SO2. The molar mass can determine the number of moles. Then use Avogodro's number to calculate the number of molecules.
Please see this video. It walks you through step by step how to do a similar problem.
Step 1. Calculate molar mass of your compound
Step 2. Divide 2.3 grams by the molar mass of NH4SO2, this gives us moles
Step 3. Multiply by Avogodro's number (6.02x10^23) this gives you molecules.