Ammonium sulfate help?

Question

14.Ammonium sulfate,(NH4)2SO4,is a common ingredient in fertilizers and is a source of nitrogen.
a.Would you calculate the atomic mass, molecular mass, or formula mass of ammonium surfate? Explain how you came to your decision.
b.What is this value for (NH4)2SO4?
c.Avogadro’s number is equal to 6.0221x10 23. How may ammonium ions are in 100.0g of ammonium sulfate?
d.You make a solution of ammonium sulfate by mixing 150 g of(NH4)2SO4 in 2.00 L of water in a beaker. What is the molariry of the resulting solution assuming that all of the solute dissolves?

Answer 1

a) Molecular mass. I need to know the amount to add.

b) Mr = 132

c) No. of molecules = 100/132 x avogadro's constant
= 4.56 x10^23

d) No. of mols = 150/132
= 1.1364mols
Molarity = 1.1364 / 2
=0.568M

Answer 2

a. Ammonium sulfate contains two polyatomic ions. These are bonded by an ionic bond so you would calculate a formula mass. (Atomic mass is a term used for just elements; molecular mass is for covalently bonded molecules).

b. Find a periodic chart and add up the individual atomic masses to get the formula mass:

(2 x N) + (8 x H) + S + (4 x O) = formula mass

c. Once you have your formula mass, divide 100.0g by that mass to get moles of ammonium sulfate. Since there are 2 ammonium ions in each molecule you would then multiply your answer by 2 to get moles of ammonium.

since 1 mole = 6.0221 x 10 23, multiply this number by your answer in #3 to get how many ammonium ions in the 100.0 g.

d. Molarity = moles/liters

first change 150 g to moles by dividing by the formula mass you found in "b".

then divide your moles by the volume and you will have molarity.