A 1.8 mole sample of a compound weighs 195 g and is found to be 11.18% H and 88.82% C. What is
the molecular formula for the compound?
Take a 100 g sample which will give you
11.18 g H and 88.82 g C.
mols C = 88.81/12 = ?
mols H = 11.18/1 = ?
Now find the ratio of the two elements to each other. I obtained C2H3.
empirical mass = 27
mols = grams/molar mass
You have moles and grams, solve for molar mass.
Then molar mass = empirical mass*y
Substitute and solve for y and from that the molecular formula.
To determine the molecular formula of the compound, we need to find the empirical formula first. The empirical formula represents the simplest whole-number ratio of the atoms present in the compound.
1. Start by calculating the number of moles of hydrogen (H) and carbon (C) in the sample.
- The sample weighs 195 g, and the compound is found to be 11.18% hydrogen (H) and 88.82% carbon (C).
- To find the moles of hydrogen, multiply the percentage of hydrogen by the total moles in the sample:
Number of moles of H = (11.18% / 100%) * 1.8 mol
- To find the moles of carbon, multiply the percentage of carbon by the total moles in the sample:
Number of moles of C = (88.82% / 100%) * 1.8 mol
2. Determine the ratio of the moles of hydrogen to carbon.
- Divide the number of moles of hydrogen by the number of moles of carbon:
H : C = (moles of H) / (moles of C)
3. Simplify the ratio to its simplest whole-number ratio.
- Divide both the numerator and denominator of the ratio by the greatest common divisor (GCD) to simplify it.
4. Use the simplest whole-number ratio to write the empirical formula.
- Use the ratio from step 3 to determine the subscripts of the elements in the empirical formula.
By following these steps, you can find the empirical formula of the compound.