empirical formula for

K 60.0% C 18.5% N 21.5%
and
P 7.5% I 92.5%

To determine the empirical formula of a compound based on the given percentages, we need to convert the percentages into moles. We will use the molar masses of the elements to do this calculation.

First, let's assume we have 100 grams of the compound.

For the first compound:
K (Potassium):
- Percentage: 60.0%
- Molar mass: 39.10 g/mol

C (Carbon):
- Percentage: 18.5%
- Molar mass: 12.01 g/mol

N (Nitrogen):
- Percentage: 21.5%
- Molar mass: 14.01 g/mol

To calculate the number of moles of each element, multiply the percentage by the molar mass and divide by 100:

Number of moles of K = (60.0/100) * (100/39.10) = 0.153 mol
Number of moles of C = (18.5/100) * (100/12.01) = 0.154 mol
Number of moles of N = (21.5/100) * (100/14.01) = 0.154 mol

To find the empirical formula, we need to find the simplest whole-number ratio between these atoms. By dividing each number of moles by the smallest number of moles (0.153), we get:

K: 0.153 mol / 0.153 = 1
C: 0.154 mol / 0.153 = 1
N: 0.154 mol / 0.153 = 1

Therefore, the empirical formula for the first compound is KCN.

For the second compound:
P (Phosphorus):
- Percentage: 7.5%
- Molar mass: 30.97 g/mol

I (Iodine):
- Percentage: 92.5%
- Molar mass: 126.90 g/mol

Using the same calculations as above, we find:

Number of moles of P = (7.5/100) * (100/30.97) = 0.024 mol
Number of moles of I = (92.5/100) * (100/126.90) = 0.729 mol

Dividing each number of moles by the smallest number (0.024), we get:

P: 0.024 mol / 0.024 = 1
I: 0.729 mol / 0.024 = 30.375

To obtain a whole-number ratio, we can multiply all atom numbers by 8:

P: 1 * 8 = 8
I: 30.375 * 8 = 243

Therefore, the empirical formula for the second compound is PI₈.

To determine the empirical formula, we need to find the simplest whole number ratio of the elements present in the compound.

1. Start by assuming we have 100 grams of the compound.
For the first compound:
- K: 60.0% of 100 grams is 60 grams.
- C: 18.5% of 100 grams is 18.5 grams.
- N: 21.5% of 100 grams is 21.5 grams.

For the second compound:
- P: 7.5% of 100 grams is 7.5 grams.
- I: 92.5% of 100 grams is 92.5 grams.

2. Convert the mass of each element to moles.
To do this, divide the mass of each element by its molar mass.
- The molar mass of K (potassium) is 39.10 g/mol.
- The molar mass of C (carbon) is 12.01 g/mol.
- The molar mass of N (nitrogen) is 14.01 g/mol.
- The molar mass of P (phosphorus) is 30.97 g/mol.
- The molar mass of I (iodine) is 126.90 g/mol.

For the first compound:
- Moles of K = 60 g / 39.10 g/mol = 1.53 mol
- Moles of C = 18.5 g / 12.01 g/mol = 1.54 mol
- Moles of N = 21.5 g / 14.01 g/mol = 1.54 mol

For the second compound:
- Moles of P = 7.5 g / 30.97 g/mol = 0.24 mol
- Moles of I = 92.5 g / 126.90 g/mol = 0.73 mol

3. Find the simplest whole number ratio by dividing the moles of each element by the smallest number of moles obtained.
For the first compound:
- Smallest number of moles = 1.53 mol, so divide all the moles by 1.53.

- Moles of K in the simplest ratio = 1.53 mol / 1.53 mol = 1
- Moles of C in the simplest ratio = 1.54 mol / 1.53 mol = 1
- Moles of N in the simplest ratio = 1.54 mol / 1.53 mol = 1

For the second compound:
- Smallest number of moles = 0.24 mol, so divide all the moles by 0.24.

- Moles of P in the simplest ratio = 0.24 mol / 0.24 mol = 1
- Moles of I in the simplest ratio = 0.73 mol / 0.24 mol = 3

4. Write the empirical formula using the whole number ratios found.

For the first compound, since the ratio is 1:1:1, the empirical formula is KCN.
For the second compound, since the ratio is 1:3, the empirical formula is PI3.

Take a 100 g sample which gives you

K = 60 g
C = 18.5 g
N = 21.5 g

Convert to mols.
mol K = 60/39.1 = ?
mol C = 18.5/12 = ?
mol N = 21.5/14 = ?

Now find the ratio of each element to each other. The easy way to do that is to divide the smallest number by itself (you know that will give you 1), then divide the other numbers by the same small number. Round to a whole number to give you KxCyNz. Post your work if you run into trouble.