Please help! I cannot figure out the steps of going from mass of Hydrogen to moles of carbon in ethanol.

Question

A sample of ethanol (C2H6O) contains 3.024g of hydrogen. How many moles of carbon are in the sample ? Molar Mass of ethanol (C2H6O)=46.07g/mol

Answer 1

Every sample of ethanol will contain 3 times as many moles of hydrogen as it does carbon (because they exist in a fixed 6 to 2 ratio, respectively). That being said, 3.024g of hydrogen is equivalent to 3 moles (3x1.008amu) of hydrogen. Therefore, we can conclude that the sample contains 1 mole of carbon.

Answer 2

First you want to calculate the Moles of Hydrogen by taking

Moles of H = Mass of H / Molar Mass of H = 3.024 g / 1.008 g/mol = 3.0 mol

Then based on the given chemical formula, there are 6 moles of hydrogen for every 1 mole of ethanol, meaning that

Moles of Ethanol = Moles of H / 6 = 3.0 mol / 6 = 0.5 mol

Finally then there are 2 moles of carbon for every 1 mole of ethanol, so you can take

Moles of C = Moles of Ethanol x 2 = 0.5 x 2 = 1.0 mol

meaning that there are 1.0 moles of carbon in the sample

Answer 3

What is the relationship of the mass of hydrogen to the moles of oxygen. The answer lies in the molecular formula of ethanol. There is a ratio of 2 molecules of carbon to every 6 molecules of hydrogen. This ratio can be extended to include for 1 mole of ethanol, there is 2 moles of carbon for every 6 moles of hydrogen. So we have the mass of a hydrogen, we need to convert this to moles and use dimensional analysis to get the moles of carbon:

3.024 g Hydrogen x ( 1 mol Hydrogen/ 1.008 g Hydrogen) x (2 mol Cabon/6 mol Hydrogen) = 1 mol Carbon

Another way to solve is that makes use of the molar mass of ethanol is as follows. In this, you will again use dimensional analysis.

3.024 g Hydrogen x (1 mol Hydrogen/ 1.008 g Hydrogen) x (1 mol ethanol/ 6 moles hydrogen) x (46.07 g/1 mol ethanol) = .23.035

23.035 g ethanol x (1 mol ethanol/ 46.07 g ethanol) x 2 mol carbon/1 mole ethanol) = 1 mole Carbon.

To be sure of the answer, ask yourself if the answer makes sense. Given that there are only three moles of hydrogen( 3.024 g Hydrogen x (1 mol Hydrogen/ 1.008 g Hydrogen)), it makes sense that since the carbon and hydrogen ratio is 1:3, carbon would have 1 mole of carbon in ethanol.

Answer 4

start by writing down the units you want for your answer: moles of carbon

next, realize that in chemistry you will often convert between mass and moles, and back again, to solve problems. and for this you will use the molar masses of compounds and elements A LOT. If the question starts with grams, and you are asked to find moles, you are going to have to use some molar masses