How many grams of water form when 5.00 g of ethanol combust with excess oxygen in the following reaction?

Question

This is the equation:

C2H6O (l) + 3 O2 (g) → 2 CO2 (g) + 3 H2O (g)

I appreciate any help!

Answer 1

Usually such qns require you to convert to moles first. The no.of moles of a substance can be obtained by dividing the mass available by its Mr (relative molecular mass). This Mr value can be obtained by adding up the Ar( relative atomic mass) of each element which is available in the periodic table.

In this case, :

Mr of Ethanol =12x2 + 1x6 + 16 = 46
No.of mol of Ethanol = 5.00/46 = 0.109 mol ( to 3 sig fig)

According to stoichiometric ratio, 1 mol of ethanol produces 3 moles of water (1:3 ratio). Since oxygen is in excess, ethanol will be the limiting agent, in which all will react. Assuming 100% yield, maximum amt of water will be produced.

Hence,

No.of mol of water produced = 3 x no. of moles of ethanol.
Mass of water produced = no.of mols of water x Mr of water
= 3 x 0.109 x 18
= 5.87g

Answer 2

Let's look at this with dimensional analysis.

You have 5.00g ethanol. You want to get to g water.

You will need to understand that each of the coefficients in the reaction represents moles of that compound needed for the reaction to take place. So, you would need 1 mol ethanol per 3 mol water.

1 mole of any molecule has what gram value? Its GMM, gram molecular mass. This is calculated by adding up the GAM (gram atomic mass) of each of the atoms in the molecule. So, for water, you would add up the GAM of two atoms of H and one atom of O.

Then, use dimensional analysis. Look below if you need the equation.

5.00g ethanol x (1mol ethanol/GMM ethanol) x (3mol water/1mol ethanol) x (GMM water/1mol water) = answer g water.

Enjoy!

Answer 3

This is a gram-gram problem.

You need to have the following information to work this problem:

1. The molar mass of 1 mole of H2O
2. The molar mass of 1 mole of C2H6O

You get this information from the periodic table by adding up the gram masses of each of the elements in the formula.

Next, you need to convert your given (5.00g H2O) to moles. KEEP IN MIND, WHEN EVERYONE ELSE IS GOING TO THE DOGS, CHEMISTS ALWAYS GO TO MOLES!

You will also use the ratio of WHAT YOU WANT over WHAT YOU HAVE from your balanced formula:

3 mol H2O
--------------
1 mol C2H6O

Then you will need to convert moles of H2O back to grams of H2O.

Set up your problem:

5.00g C2H6O x 1 mol C2H6O/ ____g C2H6O

x 3 mol H2O/1 mol C2H6O x

____g H2O/1 mol H2O =

(Put your calculated grams per mole of each of the compounds in the blanks).

Now, cancel all like units, multiply your numerators across, multiply your denominators across. Then, divide your numerator by your denominator, put in the proper number of significant digits and your units should be grams.

Hope this helps.

CHEMISTRY TEACHER

Answer 4

If my chemistry serves me right: Here's how you do it
5.00g C2H6O*1 mol C2H6O/46.06904g C2H6O * 18.01528g H2O/ 1 mol H2O *3 mol H2O/ 1 mol C2H6O=1.955 g H2O, thats your answer 1.955 g H2O