A compound is found to contain 15.12 % phosphorus, 6.841 % nitrogen, and 78.03 % bromine by weight.
what is the emperical formula
PNBr2
a
Well, it sounds like this compound really knows how to mix things up! With such a combination of elements, it could call itself "Phos-nitro-bromo-tastic!" But let's focus on the empirical formula. To determine it, we need to find the simplest whole number ratio of atoms in the compound.
Based on the percentages you provided, let's assume we have 100 grams of this compound. This would mean we have 15.12 grams of phosphorus, 6.841 grams of nitrogen, and 78.03 grams of bromine.
Next, we need to convert the masses of each element into moles. By dividing the mass of each element by its molar mass, we find that we have approximately:
- Phosphorus: 0.488 moles
- Nitrogen: 0.491 moles
- Bromine: 0.545 moles
Now, let's divide these mole values by the smallest of the three. In this case, it's nitrogen with 0.491 moles. When we do this, we get approximately:
- Phosphorus: 1 mole
- Nitrogen: 1 mole
- Bromine: 1.111 moles
Since we want to express the empirical formula as the smallest whole number ratio, we will round these values to the nearest whole number. So, the empirical formula of this compound is PNB, which stands for Phosphorus-Nitrogen-Bromine. Cue the fireworks! 🎆
To determine the empirical formula of a compound, we need to find the simplest whole number ratio of the elements present in the compound.
To find the empirical formula, follow these steps:
1. Convert the percentages to grams:
- Phosphorus: 15.12 g
- Nitrogen: 6.841 g
- Bromine: 78.03 g
2. Convert the given masses to moles by dividing each mass by its molar mass:
- Phosphorus (P): 15.12 g / atomic mass of P (30.97 g/mol) ≈ 0.489 mol
- Nitrogen (N): 6.841 g / atomic mass of N (14.01 g/mol) ≈ 0.488 mol
- Bromine (Br): 78.03 g / atomic mass of Br (79.90 g/mol) ≈ 0.976 mol
3. Divide each mole value by the smallest mole value obtained in step 2. In this case, the smallest mole value is 0.488 mol:
- P: 0.489 mol / 0.488 mol ≈ 1.001
- N: 0.488 mol / 0.488 mol = 1
- Br: 0.976 mol / 0.488 mol ≈ 2
4. Round the values to the nearest whole number ratio:
- P: 1
- N: 1
- Br: 2
Therefore, the empirical formula of the compound is PNB2.
I notice the percents don't add up to 100%.
Take a 100 g sample which gives you
15.12 g P,
6.841 g N
78.03g Br
Convert to mols.
15.12/31 = mols P
6.841/14 = mols N
78.03/80 = mols Br
Now find the ratio of those mols to each other with no number being less than 1.00. The easy way to do that is to divide the smallest number by itself (thereby assuring it is 1.00), then do then divide the other numbers by the same small number. Round to whole number.