To calculate the empirical formula and molecular formula of the compound, you need to use the information given about the combustion reaction. Let's break down the steps to solve this problem.
Step 1: Calculate the amount of carbon and hydrogen in the compound.
From the given information, we have:
12.0 g of the compound โ 5.87 g CO2
Using the molar masses, we can calculate the number of moles of CO2:
5.87 g CO2 ร (1 mol CO2 / 44.01 g CO2) = 0.133 mol CO2
Since each mole of CO2 contains one mole of carbon, we have 0.133 mol of carbon.
Next, we need to calculate the amount of hydrogen. From the reaction equation, we can see that the combustion of the compound produces water (H2O). The given information tells us that the yield of water is 1.2 g.
1.2 g of water ร (1 mol water / 18.02 g water) = 0.0666 mol water
Since each mole of water contains two moles of hydrogen, we have 0.133 mol of hydrogen.
Step 2: Calculate the amount of oxygen in the compound.
To find the amount of oxygen, we subtract the mass of carbon and hydrogen from the total mass of the compound.
Total mass of the compound = 12.0 g
Mass of carbon = 0.133 mol ร (12.01 g/mol) = 1.60 g
Mass of hydrogen = 0.133 mol ร (1.01 g/mol) = 0.134 g
Mass of oxygen = Total mass of the compound - Mass of carbon - Mass of hydrogen
Mass of oxygen = 12.0 g - 1.60 g - 0.134 g = 10.27 g
Step 3: Calculate the molar ratios.
Now that we have the amounts of each element, we need to find the simplest whole-number ratio between them. Divide the moles of each element by the smallest number of moles.
Carbon: 0.133 mol / 0.133 mol = 1 (rounded to the nearest whole number)
Hydrogen: 0.133 mol / 0.133 mol = 1 (rounded to the nearest whole number)
Oxygen: 10.27 g / 16.00 g/mol = 0.644 mol / 0.133 mol = 4.85 (rounded to the nearest whole number)
The empirical formula of the compound is CH4O5.
Step 4: Calculate the molecular formula.
To find the molecular formula, we need to determine the molar mass of the empirical formula. The given information states that the molecular mass is approximately 90 g/mol.
The empirical formula mass:
C: 12.01 g/mol ร 1 = 12.01 g/mol
H: 1.01 g/mol ร 4 = 4.04 g/mol
O: 16.00 g/mol ร 5 = 80.00 g/mol
Adding these masses together, we get:
12.01 g/mol + 4.04 g/mol + 80.00 g/mol = 96.05 g/mol
To find the molecular formula, divide the molecular mass provided (90 g/mol) by the empirical formula mass (96.05 g/mol) to determine the multiplier:
90 g/mol รท 96.05 g/mol โ 0.936
Multiply the subscripts in the empirical formula by the multiplier to get the molecular formula:
C1H4O5 ร 0.936 = C0.936H3.744O4.68
Rounding to the nearest whole number, we get the molecular formula as C1H4O5.
So, the empirical formula is CH4O5, and the molecular formula is C1H4O5.