Question

How many grams of water can be produced when 11.7 moles of ethane (C2H6) react with excess oxygen gas? Unbalanced equation: C2H6 + O2 ----> CO2 + H2O Show, or explain, all of your work along with the final answer.

Answer 1

@iPwnBunnies

Answer 2

balanced equation: 2C2H6 + 7O2 --> 4CO2 + 6H2O

Answer 3

This is easy man. Look at the equation. Use stoichiometry (mole ratios). What's the ratio of water to ethane?

Answer 4

2:6?

Answer 5

or the other way round?

Answer 6

Other way around. 6 mol H20/2 mol C2H6

Answer 7

oh ok

Answer 8

This is saying we can make 6 moles of water if we have 2 moles of ethane (w/ unlimited O2).

Answer 9

ok

Answer 10

So, go back to your problem. We have 11.7 moles of ethane. Can you do some math with the mole ratio to figure out how many moles of water that can make?

Answer 11

maybe?

Answer 12

Yes, you can lol.

Answer 13

You have 11.7 moles ethane and the mole ratio 2 moles of H2O to 6 moles of ethane.

Answer 14

11.7g C2H6 x 6/2

Answer 15

There ya go man. That'll give us the amount of moles of water that can be made from 11.7 moles of ethane and excess O2.

Answer 16

35.1g

Answer 17

Wrong. We'll have 35.1 moles of H2O. Don't mess it up. We use mole ratios in chemical equations to figure out how many MOLES something has.

Answer 18

ok

Answer 19

To find the mass, we have to multiply the amount of moles by the molar mass. Do you know the molar mass of H2O? You can find it with the Periodic Table.

Answer 20

18.01?

Answer 21

since it's 1.0079 x 2 + 15.999 right?

Answer 22

Yes. H20 has a molar mass of 18.01 grams per mol.

Answer 23

ok

Answer 24

Can you figure out the mass of 35.1 moles of H2O now?

Answer 25

how do i dot that?

Answer 26

Check out the units of both. How can we cancel out the moles and be left with grams?

Answer 27

Wrong.

Answer 28

;P

Answer 29

If 18.01 grams is the mass of one mole, how much will 35.1 moles be?

Answer 30

1.95g?

Answer 31

\[(35.1 mol H2O)(18.01 \frac{grams}{mol}) =\]

Answer 32

35.1/18.01

Answer 33

is it x?

Answer 34

Why would you divide. Look at the units man. The units tell you the answer. You can solve lots of problems looking at the units. Yes, multiply.

Answer 35

ok

Answer 36

And, i don't know, I'm obsessed with division i guess...

Answer 37

wait,35.01 x 18.01?

Answer 38

is it 632.2

Answer 39

Yeah. 35.01 moles times 18.01 grams per mol.

Answer 40

Sure.

Answer 41

i DON T UNDERSTAND... ;(

Answer 42

35.1 moles*
How do you not understand? I literally explained it as clear as I can.

Answer 43

jk

Answer 44

so it is 632.2?

Answer 45

No. That's a number.

Answer 46

We want to know the mass of the water. Use units.

Answer 47

ok

Answer 48

...

Answer 49

i keep getting that!! 632.2g

Answer 50

Good.

Answer 51

why is it good?

Answer 52

well thanks i guess! ;)