Imagine there is a tank of unknown gas that contains 53.31% carbon, 35.51% oxygen, and 11.18% hydrogen by mass. At 35.0 °C and 0.470 bar, 2.0 L of the gas has a mass of 3.3 g. Using this information, answer the following questions. a.) What is the empirical formula of the gas?
assume 100 grams
then moles C= 53.31/12
moles O2=35.51/32
moles H= 11.18/2
now, divide each of those numbers by the smallest one. you may have to adjust the ratios to make them all whole numbers.
The remaining numbers are the mole ratios in the formula CxOyHz
This answer differs from the other answer you have. I will estimate for the following:
mols of each = grams/ATOMIC MASS or
53.31/12 = 4.44
35.51/16 = 2.22
11.18/1 = 11.2
To find the empirical formula you want the ratio of the elements to each other with the smallest number being 1.00. The easy to do this is to divide the smallest number by itself and divide all of the other numbers by the smallest number. That gives me
O = 2.22/2.22 = 1
C = 4.44/2.22 = 2
H = 11.18/2.22 = 5.04 and this is rounded to a whole number of 5.00
Empirical formula is C2H5O.
You don't need the other information in the problem for the empirical formula; I suspect you did not type in part b question which would be to calculate the molecular formula of the compound. You need that other information to find the molar mass of C2H5O.
dr Bob is correct on the atomic masses, I wasn't thinking.
To determine the empirical formula of the unknown gas, we need to find the ratio of the number of atoms of each element present in the compound.
Given:
- The composition of the gas by mass is 53.31% carbon, 35.51% oxygen, and 11.18% hydrogen.
- The gas has a mass of 3.3 g and occupies a volume of 2.0 L at 35.0 °C and 0.470 bar.
1. Convert the mass percentage of each element to grams:
- Carbon: (53.31/100) * 3.3 g = 1.757 g
- Oxygen: (35.51/100) * 3.3 g = 1.169 g
- Hydrogen: (11.18/100) * 3.3 g = 0.368 g
2. Convert grams to moles using the molecular weight of each element:
- Carbon: 1.757 g / 12.0 g/mol = 0.1464 mol
- Oxygen: 1.169 g / 16.0 g/mol = 0.0731 mol
- Hydrogen: 0.368 g / 1.0 g/mol = 0.368 mol
3. Find the ratio of the moles of each element by dividing each value by the smallest number of moles:
- Carbon: 0.1464 mol / 0.0731 mol = 2
- Oxygen: 0.0731 mol / 0.0731 mol = 1
- Hydrogen: 0.368 mol / 0.0731 mol = 5
4. Use the ratio of atoms to write the empirical formula:
- The empirical formula of the gas is C2H5O.
Therefore, the empirical formula of the gas is C2H5O.