Washing soda (or sodium carbonate, Na2CO3) has a molar mass of 105.988 g. How many moles of sodium are there in 46 grams of washing soda?
The Correct Answer and Explanation is:
To determine how many moles of sodium are present in 46 grams of washing soda (sodium carbonate, Na2CO3), we need to follow these steps:
Step 1: Find the molar mass of Na2CO3
The chemical formula for washing soda is Na2CO3, which means it contains:
- 2 sodium (Na) atoms
- 1 carbon (C) atom
- 3 oxygen (O) atoms
The atomic masses (approximate) are:
- Sodium (Na): 22.99 g/mol
- Carbon (C): 12.01 g/mol
- Oxygen (O): 16.00 g/mol
Now, let’s calculate the molar mass of Na2CO3:Molar mass of Na2CO3=(2×22.99)+(1×12.01)+(3×16.00)\text{Molar mass of Na2CO3} = (2 \times 22.99) + (1 \times 12.01) + (3 \times 16.00) Molar mass of Na2CO3=(2×22.99)+(1×12.01)+(3×16.00)=45.98+12.01+48.00=105.99 g/mol= 45.98 + 12.01 + 48.00 = 105.99 \, \text{g/mol}=45.98+12.01+48.00=105.99g/mol
This confirms the molar mass is approximately 105.99 g/mol.
Step 2: Determine the number of moles of Na2CO3 in 46 grams
To find the number of moles of Na2CO3 in 46 grams, we use the formula:moles of Na2CO3=massmolar mass\text{moles of Na2CO3} = \frac{\text{mass}}{\text{molar mass}} moles of Na2CO3=molar massmassmoles of Na2CO3=46 g105.99 g/mol≈0.4346 mol\text{moles of Na2CO3} = \frac{46 \, \text{g}}{105.99 \, \text{g/mol}} \approx 0.4346 \, \text{mol}moles of Na2CO3=105.99g/mol46g≈0.4346mol
Step 3: Determine the number of moles of sodium (Na)
Since each formula unit of Na2CO3 contains 2 sodium (Na) atoms, the number of moles of sodium is:moles of Na=2×moles of Na2CO3\text{moles of Na} = 2 \times \text{moles of Na2CO3}moles of Na=2×moles of Na2CO3moles of Na=2×0.4346 mol=0.8692 mol\text{moles of Na} = 2 \times 0.4346 \, \text{mol} = 0.8692 \, \text{mol}moles of Na=2×0.4346mol=0.8692mol
Conclusion:
In 46 grams of washing soda, there are approximately 0.869 moles of sodium.
