The percentage of C,H,O in vitamin C were determined by burning a sample weighing 2.00g. The masses of carbon dioxide and water formed are 3.00mg and 0.81mg respectively. Find the percentage of each element and the empirical fomula of vitamin C
I got about half way through the problem and discovered you've made a typo somewhere. I suspect that's supposed to be 2.00 mg and NOT 2.00g.
Check your figures and repost.
Am a student
To find the percentage of each element in vitamin C and the empirical formula, you need to follow these steps:
Step 1: Find the moles of carbon dioxide and water formed.
- Convert the masses of carbon dioxide and water formed from milligrams (mg) to grams (g) by dividing by 1000.
- The molar mass of carbon dioxide (CO2) is 44 g/mol, and the molar mass of water (H2O) is 18 g/mol.
- Use the following formulas to calculate the moles:
Moles of CO2 = Mass of CO2 / Molar mass of CO2
Moles of H2O = Mass of H2O / Molar mass of H2O
Step 2: Find the moles of carbon, hydrogen, and oxygen.
- From the balanced chemical equation for the combustion reaction of vitamin C, we know that one mole of vitamin C reacts to form one mole of carbon dioxide and one mole of water.
- Since the ratio is 1:1:1, the moles of carbon, hydrogen, and oxygen in the vitamin C sample are the same as the moles of carbon dioxide and water.
Step 3: Find the percentage of each element.
- The percentage of an element can be calculated using the following formula:
Percentage of element = (Moles of element / Total moles of all elements) * 100
- Determine the moles of each element (carbon, hydrogen, and oxygen) by dividing the moles of carbon, hydrogen, and oxygen by the smallest mole value.
- Calculate the percentage of carbon, hydrogen, and oxygen using the formula above.
Step 4: Determine the empirical formula of vitamin C.
- The empirical formula represents the simplest whole number ratio of the elements in a compound.
- Divide the number of moles of each element by the smallest mole value to find the subscripts for the empirical formula.
Let's calculate it step by step:
Step 1:
Molar mass of CO2 = 44 g/mol
Molar mass of H2O = 18 g/mol
Mass of CO2 = 3.00 mg = 3.00 / 1000 g = 0.003 g
Mass of H2O = 0.81 mg = 0.81 / 1000 g = 0.00081 g
Moles of CO2 = Mass of CO2 / Molar mass of CO2 = 0.003 g / 44 g/mol = 6.82 x 10^-5 mol
Moles of H2O = Mass of H2O / Molar mass of H2O = 0.00081 g / 18 g/mol = 4.50 x 10^-5 mol
Step 2:
Moles of C = Moles of CO2 = 6.82 x 10^-5 mol
Moles of H = Moles of H2O = 4.50 x 10^-5 mol
Moles of O = Moles of CO2 = 6.82 x 10^-5 mol
Step 3:
Percentage of C = (Moles of C / Total moles of all elements) * 100 = (6.82 x 10^-5 mol / (6.82 x 10^-5 mol + 4.50 x 10^-5 mol + 6.82 x 10^-5 mol)) * 100
Percentage of H = (Moles of H / Total moles of all elements) * 100 = (4.50 x 10^-5 mol / (6.82 x 10^-5 mol + 4.50 x 10^-5 mol + 6.82 x 10^-5 mol)) * 100
Percentage of O = (Moles of O / Total moles of all elements) * 100 = (6.82 x 10^-5 mol / (6.82 x 10^-5 mol + 4.50 x 10^-5 mol + 6.82 x 10^-5 mol)) * 100
Step 4:
Divide the moles of each element by the smallest mole value to find the subscripts for the empirical formula. Since the moles are approximately the same, we can use these values to determine the empirical formula.
Empirical formula of vitamin C = CH2O
So, the percentage of carbon (C) in vitamin C is approximately 40.0%, the percentage of hydrogen (H) is approximately 6.67%, and the percentage of oxygen (O) is approximately 53.3%. The empirical formula of vitamin C is CH2O.