Answer :
To calculate the molar mass of \( \text{Li}_2\text{S} \) correctly, follow these detailed steps:
1. Determine the molar masses of the individual elements:
- Lithium (\( \text{Li} \)) has a molar mass of 6.94 g/mol.
- Sulfur (\( \text{S} \)) has a molar mass of 32.06 g/mol.
2. Understand the chemical formula \(\text{Li}_2\text{S}\):
- The subscript "2" in \(\text{Li}_2\) indicates that there are 2 moles of lithium atoms.
- There is no subscript after sulfur (\(\text{S}\)), which implies that there is 1 mole of sulfur atom.
3. Calculate the total mass:
- The total mass contributed by lithium is the molar mass of lithium multiplied by the number of moles of lithium: \(2 \times 6.94 \text{ g/mol}\).
- The total mass contributed by sulfur is the molar mass of sulfur, which is \(32.06 \text{ g/mol}\).
4. Add these masses together:
[tex]\[ (2 \times 6.94) \text{ g/mol} + 32.06 \text{ g/mol} \][/tex]
5. Perform the addition:
[tex]\[ 13.88 \text{ g/mol} + 32.06 \text{ g/mol} = 45.94 \text{ g/mol} \][/tex]
Therefore, the molar mass of \(\text{Li}_2\text{S}\) is 45.94 g/mol.
Given the options:
- F: Add the masses of 1 mole of lithium and 2 moles of sulfur (incorrect).
- G: Add the masses of 1 mole of lithium and 1 mole of sulfur (incorrect).
- H: Add the masses of 2 moles of lithium and 1 mole of sulfur (correct).
- J: Add the masses of 2 moles of lithium and 2 moles of sulfur (incorrect).
The correct process is described in option H: Add the masses of 2 moles of lithium and 1 mole of sulfur.
1. Determine the molar masses of the individual elements:
- Lithium (\( \text{Li} \)) has a molar mass of 6.94 g/mol.
- Sulfur (\( \text{S} \)) has a molar mass of 32.06 g/mol.
2. Understand the chemical formula \(\text{Li}_2\text{S}\):
- The subscript "2" in \(\text{Li}_2\) indicates that there are 2 moles of lithium atoms.
- There is no subscript after sulfur (\(\text{S}\)), which implies that there is 1 mole of sulfur atom.
3. Calculate the total mass:
- The total mass contributed by lithium is the molar mass of lithium multiplied by the number of moles of lithium: \(2 \times 6.94 \text{ g/mol}\).
- The total mass contributed by sulfur is the molar mass of sulfur, which is \(32.06 \text{ g/mol}\).
4. Add these masses together:
[tex]\[ (2 \times 6.94) \text{ g/mol} + 32.06 \text{ g/mol} \][/tex]
5. Perform the addition:
[tex]\[ 13.88 \text{ g/mol} + 32.06 \text{ g/mol} = 45.94 \text{ g/mol} \][/tex]
Therefore, the molar mass of \(\text{Li}_2\text{S}\) is 45.94 g/mol.
Given the options:
- F: Add the masses of 1 mole of lithium and 2 moles of sulfur (incorrect).
- G: Add the masses of 1 mole of lithium and 1 mole of sulfur (incorrect).
- H: Add the masses of 2 moles of lithium and 1 mole of sulfur (correct).
- J: Add the masses of 2 moles of lithium and 2 moles of sulfur (incorrect).
The correct process is described in option H: Add the masses of 2 moles of lithium and 1 mole of sulfur.
