in an experiment a sample of hydrocarbon was analyzed. The sample contained6 g of carbon and 1.344 g Hydrogen.
a) whats the empirical formula?
the density of hydrocarbon at 25 C and 1.09 atm is 1.96 g/L
b.) whats the molar mass of the hydrocarbon?
c) whats the molecular formula?
1. Calculate percent C and percent H.
2. Take a 100 g sample, and convert percent to grams C and H.
3. Convert grams to moles C and moles H. moles = grams/atomic mass.
4. Find the ratio of C and H to each other in small whole numbers. The easy way to do that is to divide the smaller value by itself; then divide the other number by the same small number. Round to whole numbers but don't round if the value is more than 0.1 away from a whole number. In that case, multiply each number by a factor (2x, 3x, 4x, 5x etc) until you obtain two whole numbers within rounding of 0.1.
b. After the formula is obtained, just add the atomic masses.
c. Use PV = nRT. For density that is
P*molar mass = density*R*T.
Post your work if you stuck.
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To determine the empirical formula of a compound, we need to find the simplest ratio between the elements present. In this case, we have 6 grams of carbon and 1.344 grams of hydrogen.
a) Calculation of the empirical formula:
1. Determine the moles of each element:
Moles of carbon (C) = mass of carbon / atomic mass of carbon
= 6 g / 12.01 g/mol (atomic mass of carbon)
= 0.4996 mol
Moles of hydrogen (H) = mass of hydrogen / atomic mass of hydrogen
= 1.344 g / 1.008 g/mol (atomic mass of hydrogen)
= 1.334 mol
2. Simplify the mole ratio:
Divide both moles by the lowest number of moles to obtain the simplest ratio.
In this case, the lowest number of moles is 0.4996 mol.
Therefore, dividing both moles by 0.4996, we get approximately:
C: 0.4996 mol / 0.4996 mol ≈ 1
H: 1.334 mol / 0.4996 mol ≈ 2.67
Taking into account significant figures, we can approximate the ratio to:
C: 1
H: 2.7 (rounded to one decimal place)
Therefore, the empirical formula of the hydrocarbon is CH2.7 (or approximated to CH3).
b) Calculation of the molar mass:
To calculate the molar mass of the hydrocarbon, we sum the atomic masses of carbon and hydrogen in the empirical formula.
- Atomic mass of carbon (C) = 12.01 g/mol
- Atomic mass of hydrogen (H) = 1.008 g/mol
Molar mass = (Mass of carbon x Atomic mass of carbon) + (Mass of hydrogen x Atomic mass of hydrogen)
= (6 g x 12.01 g/mol) + (1.344 g x 1.008 g/mol)
= 72.06 g/mol + 1.3532 g/mol
= 73.4132 g/mol
The molar mass of the hydrocarbon is approximately 73.4 g/mol.
c) Calculation of the molecular formula:
To determine the molecular formula, we compare the molar mass of the empirical formula with the given molar mass (73.4132 g/mol).
Let's assume the molecular formula of the hydrocarbon is (CH2.7)n, where n is the number of empirical formula units.
Molar mass of the molecular formula = (Molar mass of empirical formula) x n
73.4132 g/mol = (12.01 g/mol + 2.7 g/mol) x n
73.4132 g/mol = 14.71 g/mol x n
n ≈ 4.9947
Since n is not a whole number, we round it to the nearest whole number, giving n = 5.
Therefore, the molecular formula of the hydrocarbon is approximately (CH2.7)5, which can be further simplified as C5H13.