Question

In an experiment 2.810 g of magnesium is reacted with 2.220 g of oxygen gas according to the equation:
Mg + O2 ==> MgO.

A. What is the limiting reactant?
B. What mass of the other reactant is in excess?
C. What mass of MgO is produced?

Answer 1

Welcome to OpenStudy. First, make sure the equation is balanced. Next, can you find the number of moles of whatever substance you have?

Use this: http://www.ptable.com/

Answer 2

The balanced equation is 2Mg + O2 -> 2MgO

The number of moles of magnesium is 0.1156
The number moles of oxygen is 0.0694

And thank you :)

Answer 3

Looks great so far. Can you use stoichiometry on both of those numbers of moles to determine which one would produce less MgO?

Answer 4

The one that produces less of the product will be "used up" first in the reaction and would be the limiting reactant.

Answer 5

For magnesium: 4.66 g MgO
For oxygen: 5.59 g Mg)

So magnesium would be the limiting reactant, and that answers A. :D

Answer 6

MgO, oops

Answer 7

Awesome! :) You can get c directly...

Answer 8

Great! I'm a bit confused for what to do for B, though :P

Answer 9

Ok, that one takes a bit more work. Can you take the amount of MgO produced and back-calculate the amount of O2 consumed?

Answer 10

In excess means left over.

Answer 11

That is MgO produced from the limiting reactant.

Answer 12

1.85 g of O2 were consumed. :3

Answer 13

Great! So, if you started with 2.22g and 1.85 were consumed, how many do you have left over?

Answer 14

0.37 g :)

Answer 15

:)

Answer 16

I'll try those answers again, since I've gotten the same answers, and my homework program says I'm wrong :P

Answer 17

Hmm, are you watching sig figs?

Answer 18

Looks like the problem has 4 sig figs.

Answer 19

Ah, now it went through :D Thanks so much! :)

Answer 20

No worries. Keep up the good work!

Answer 21

Sorry my housemate needed urgent help with something. Good job you two :) Welcome again to OS Anita. Do take time to read our CoC: http://openstudy.com/code-of-conduct and enjoy your stay. If you are satisfied with any question, please reward a medal to whoever you think deserves it and close the question. We also have a fan and testimony system. See you around :)

Answer 22

Thanks, wolfe! :)