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To determine the formula mass, we sum the atomic masses of all atoms in the chemical formula. We will use the following approximate atomic masses:

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5 parts
a

53.50 g/mol\text{53.50 g/mol}

b

84.01 g/mol\text{84.01 g/mol}

c

162.20 g/mol\text{162.20 g/mol}

d

46.08 g/mol\text{46.08 g/mol}

e

342.17 g/mol\text{342.17 g/mol}

Step-by-step solution

10 steps

To determine the formula mass, we sum the atomic masses of all atoms in the chemical formula. We will use the following approximate atomic masses:
N = 14.01 g/mol
H = 1.01 g/mol
Cl = 35.45 g/mol
Na = 22.99 g/mol
C = 12.01 g/mol
O = 16.00 g/mol
Fe = 55.85 g/mol
Al = 26.98 g/mol
S = 32.07 g/mol

Part a· 2 steps

NH4Cl\text{NH}_4\text{Cl}

  1. Identify the number of atoms for each element.

    1 nitrogen (N) atom, 4 hydrogen (H) atoms, 1 chlorine (Cl) atom.

  2. Calculate the total mass.

    Formula mass=(1×14.01)+(4×1.01)+(1×35.45)\text{Formula mass} = (1 \times 14.01) + (4 \times 1.01) + (1 \times 35.45) Formula mass=14.01+4.04+35.45\text{Formula mass} = 14.01 + 4.04 + 35.45 Formula mass=53.50 g/mol\text{Formula mass} = 53.50 \text{ g/mol}

    The formula mass of NH4Cl\text{NH}_4\text{Cl} is 53.50 g/mol\boxed{\text{53.50 g/mol}}.

Part b

84.01 g/mol\text{84.01 g/mol}

NaHCO3\text{NaHCO}_3

  1. Identify the number of atoms for each element.

    1 sodium (Na) atom, 1 hydrogen (H) atom, 1 carbon (C) atom, 3 oxygen (O) atoms.

  2. Calculate the total mass.

    Formula mass=(1×22.99)+(1×1.01)+(1×12.01)+(3×16.00)\text{Formula mass} = (1 \times 22.99) + (1 \times 1.01) + (1 \times 12.01) + (3 \times 16.00) Formula mass=22.99+1.01+12.01+48.00\text{Formula mass} = 22.99 + 1.01 + 12.01 + 48.00 Formula mass=84.01 g/mol\text{Formula mass} = 84.01 \text{ g/mol}

    The formula mass of NaHCO3\text{NaHCO}_3 is 84.01 g/mol\boxed{\text{84.01 g/mol}}.

Part c

162.20 g/mol\text{162.20 g/mol}

FeCl3\text{FeCl}_3

  1. Identify the number of atoms for each element.

    1 iron (Fe) atom, 3 chlorine (Cl) atoms.

  2. Calculate the total mass.

    Formula mass=(1×55.85)+(3×35.45)\text{Formula mass} = (1 \times 55.85) + (3 \times 35.45) Formula mass=55.85+106.35\text{Formula mass} = 55.85 + 106.35 Formula mass=162.20 g/mol\text{Formula mass} = 162.20 \text{ g/mol}

    The formula mass of FeCl3\text{FeCl}_3 is 162.20 g/mol\boxed{\text{162.20 g/mol}}.

Part d

46.08 g/mol\text{46.08 g/mol}

C2H5OH\text{C}_2\text{H}_5\text{OH}

  1. Identify the number of atoms for each element.

    2 carbon (C) atoms, 6 hydrogen (H) atoms (5 in C2H5\text{C}_2\text{H}_5 and 1 in OH), 1 oxygen (O) atom.

  2. Calculate the total mass.

    Formula mass=(2×12.01)+(6×1.01)+(1×16.00)\text{Formula mass} = (2 \times 12.01) + (6 \times 1.01) + (1 \times 16.00) Formula mass=24.02+6.06+16.00\text{Formula mass} = 24.02 + 6.06 + 16.00 Formula mass=46.08 g/mol\text{Formula mass} = 46.08 \text{ g/mol}

    The formula mass of C2H5OH\text{C}_2\text{H}_5\text{OH} is 46.08 g/mol\boxed{\text{46.08 g/mol}}.

Part e

342.17 g/mol\text{342.17 g/mol}

Al2(SO4)3\text{Al}_2(\text{SO}_4)_3

  1. Identify the number of atoms for each element.

    2 aluminium (Al) atoms, 3 sulfur (S) atoms (from 3×S3 \times \text{S}), 12 oxygen (O) atoms (from 3×4×O3 \times 4 \times \text{O}).

  2. Calculate the total mass.

    Formula mass=(2×26.98)+(3×32.07)+(12×16.00)\text{Formula mass} = (2 \times 26.98) + (3 \times 32.07) + (12 \times 16.00) Formula mass=53.96+96.21+192.00\text{Formula mass} = 53.96 + 96.21 + 192.00 Formula mass=342.17 g/mol\text{Formula mass} = 342.17 \text{ g/mol}

    The formula mass of Al2(SO4)3\text{Al}_2(\text{SO}_4)_3 is 342.17 g/mol\boxed{\text{342.17 g/mol}}.

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