i need a bit of help finding out how to do this problem. just tell me how and ill take it from there.
Q.A compound containing carbon, hydrogen, and Oxygen is found to be 40% carbon and 6.7% hydrogen by mass. the molar mass of this compound is between 115 g / mol. determine the molecular formula for the compound
Use the percents as grams, find moles of each, divide by lowest number of moles to find the ratio for each. This is your empirical. Then find the molar mass of the compound and divide by 115.
marty mcfly?! R u from the future? or the past?
To determine the molecular formula of a compound given the percentage composition and molar mass, you need to follow a step-by-step process.
Step 1: Convert the percentages into grams.
Using the given percentages, assume you have 100 grams of the compound. Therefore, the compound contains:
- 40 grams of carbon (40% of 100 g)
- 6.7 grams of hydrogen (6.7% of 100 g)
- The remaining mass must be oxygen (since the compound only contains carbon, hydrogen, and oxygen)
Step 2: Convert grams into moles.
To convert grams into moles, divide the mass of each element by its molar mass. You can find the molar mass of elements on the periodic table.
- Carbon (C): The molar mass of carbon is 12.01 g/mol. Divide the mass of carbon (40 g) by its molar mass:
Moles of carbon = 40 g / 12.01 g/mol
- Hydrogen (H): The molar mass of hydrogen is 1.01 g/mol. Divide the mass of hydrogen (6.7 g) by its molar mass:
Moles of hydrogen = 6.7 g / 1.01 g/mol
- Oxygen (O): Since the remaining mass is oxygen, subtract the total mass of carbon and hydrogen from the initial 100 grams:
Mass of oxygen = (100 g - 40 g - 6.7 g)
Step 3: Determine the empirical formula.
The empirical formula represents the simplest whole-number ratio of atoms in a compound. In this case, it gives the ratio of carbon, hydrogen, and oxygen atoms.
- Divide the moles of each element by the smallest number of moles:
Carbon: Moles of carbon / smallest mole number
Hydrogen: Moles of hydrogen / smallest mole number
Oxygen: Moles of oxygen / smallest mole number
- Round any resulting decimal values to the nearest whole number to obtain the simplest, whole-number ratio. This will give you the empirical formula.
Step 4: Find the molar mass of the empirical formula.
To find the molar mass of the empirical formula, multiply the molar masses of each element by their respective subscript in the empirical formula and add them together.
Step 5: Determine the molecular formula.
Divide the given molar mass (115 g/mol) by the molar mass of the empirical formula. This will give you the ratio "n," which represents the number of empirical formula units in the molecular formula.
Finally, multiply the subscripts in the empirical formula by "n" to obtain the molecular formula.
By following these steps, you can determine the molecular formula for the compound.