F.4 Chemisty,,,Reacting Masses!!!救我~聽日交"

Question

1. A compound has the formular of X2(SO4)3.Its molar mass is 342.3 g mol^ -1.
Calculate the relative atomic mass of element X .

2. There is 4.0 g of ammonium nitrate.

(a). Calculate the number of moles of ammonium nitrate.

(b). Calculate the number of nitrogen atoms.

(c). Calculate the number of hydrogen atoms.

(d). Calculate the total number of atoms.

Answer 1

1.
Let relative atomic mass of X = A
Molar mass of X2(SO4)3 = 2A+3(32.1+4x16) = 342.3 (g mol^-1)
Hence, relative atomic mass of X, A = 27

2.
(a)
Molar mass of NH4NO3 = 14x2 + 4x1 + 3x16 = 80
No. of moles of NH4NO3 = 4/80 = 0.05 (mol)

(b)
In each moles of NH4NO3, there are 2 moles of N atoms.
No. of moles of N atoms = 2(0.05) = 0.1 (mol)

(c)
In each moles of NH4NO3, there are 4 moles of H atoms.
No. of moles of H atoms = 4(0.05) = 0.2 (mol)

(d)
In each moles of NH4NO3, there are 9 moles of atoms.
No. of moles of atoms = 9(0.05) = 0.45 (mol)