Answer :
Let's find the empirical formulas for the given compounds using their percentages.
### Part (a)
For the compound containing sodium (Na) and chlorine (Cl), we have:
- 39.3% Na
- 60.7% Cl
Step 1: Determine the moles of each element.
To find moles, divide the percentage by the atomic mass of the element. The atomic masses are approximately:
- Na: 22.99 g/mol
- Cl: 35.45 g/mol
Calculate moles:
- Moles of Na = 39.3 / 22.99 ≈ 1.71
- Moles of Cl = 60.7 / 35.45 ≈ 1.71
Step 2: Determine the simplest whole number ratio.
Find the smallest number of moles and divide all mole values by this number:
- Both Na and Cl have approximately 1.71 moles.
- Divide both by 1.71:
- Na: 1.71 / 1.71 = 1
- Cl: 1.71 / 1.71 = 1
The empirical formula is NaCl.
### Part (b)
For the compound containing potassium (K), carbon (C), and oxygen (O), we have:
- 56.5% K
- 8.7% C
- 34.8% O
Step 1: Determine the moles of each element.
The atomic masses are:
- K: 39.10 g/mol
- C: 12.01 g/mol
- O: 16.00 g/mol
Calculate moles:
- Moles of K = 56.5 / 39.10 ≈ 1.45
- Moles of C = 8.7 / 12.01 ≈ 0.72
- Moles of O = 34.8 / 16.00 ≈ 2.18
Step 2: Determine the simplest whole number ratio.
Find the smallest number of moles and divide all mole values by this number (smallest is approximately 0.72):
- K: 1.45 / 0.72 ≈ 2
- C: 0.72 / 0.72 = 1
- O: 2.18 / 0.72 ≈ 3
The empirical formula is K2CO3.
These calculations give us the empirical formulas NaCl and K2CO3 for parts (a) and (b), respectively.
### Part (a)
For the compound containing sodium (Na) and chlorine (Cl), we have:
- 39.3% Na
- 60.7% Cl
Step 1: Determine the moles of each element.
To find moles, divide the percentage by the atomic mass of the element. The atomic masses are approximately:
- Na: 22.99 g/mol
- Cl: 35.45 g/mol
Calculate moles:
- Moles of Na = 39.3 / 22.99 ≈ 1.71
- Moles of Cl = 60.7 / 35.45 ≈ 1.71
Step 2: Determine the simplest whole number ratio.
Find the smallest number of moles and divide all mole values by this number:
- Both Na and Cl have approximately 1.71 moles.
- Divide both by 1.71:
- Na: 1.71 / 1.71 = 1
- Cl: 1.71 / 1.71 = 1
The empirical formula is NaCl.
### Part (b)
For the compound containing potassium (K), carbon (C), and oxygen (O), we have:
- 56.5% K
- 8.7% C
- 34.8% O
Step 1: Determine the moles of each element.
The atomic masses are:
- K: 39.10 g/mol
- C: 12.01 g/mol
- O: 16.00 g/mol
Calculate moles:
- Moles of K = 56.5 / 39.10 ≈ 1.45
- Moles of C = 8.7 / 12.01 ≈ 0.72
- Moles of O = 34.8 / 16.00 ≈ 2.18
Step 2: Determine the simplest whole number ratio.
Find the smallest number of moles and divide all mole values by this number (smallest is approximately 0.72):
- K: 1.45 / 0.72 ≈ 2
- C: 0.72 / 0.72 = 1
- O: 2.18 / 0.72 ≈ 3
The empirical formula is K2CO3.
These calculations give us the empirical formulas NaCl and K2CO3 for parts (a) and (b), respectively.