Question

If 4.88 grams of Zn reacts with 5.03 grams of S8 to produce 6.02 grams of ZnS, what are the theoretical yield and percent yield of this reaction? Be sure to show the work that you did to solve this problem.

unbalanced equation: Zn + S8 yields ZnS

Someone please help me!!!

Answer 1

first and most important, balance the equation

Answer 2

Yep, @JFraser is right. Do you know how to balance, @firesquad ?

Answer 3

Balanced equation: 8Zn + S8 ---> 8ZnS

Answer 4

@JFraser @JoannaBlackwelder

Answer 5

Yep, good. Percent yield = (actual/theoretical)*100

Answer 6

Actual is the amount of product given in the problem.

Answer 7

Theoretical is the amount of product found using stoichiometry from the amount of reactant given.

Answer 8

*from the amount of limiting reactant

Answer 9

I am stuck right here
4.88 g Zn x (1 mol Zn/ 65.38 g Zn) = 0.07464 mol Zn
5.03 g S8 x (1 mol S8/ 256.48 g S8) = 0.01961 mol S8

Answer 10

Ok, now use the molar ratios from the balanced reaction to convert to moles of ZnS

Answer 11

what do i do after

Answer 12

For both calculations.

Answer 13

would the ratio be 1: 8

Answer 14

For S8:ZnS, yes

Answer 15

But not for Zn:ZnS

Answer 16

0.07464 mol Zn * (1/1)= 0.07464 mol Zn
0.01961 mol S8 * (8/1) = 0.1569 mol S8
is that how to do it

Answer 17

Well, that looks good for everything but the units at the end.

Answer 18

What do I have to change for the units?

Answer 19

0.07464 mol ZnS
0.1569 mol ZnS

Answer 20

See why I did that?

Answer 21

Oh Ok, now I find the percent yield right?

Answer 22

Well, we need to first determine which value of product to go with.

Answer 23

This is the limiting reactant part. Do you know how to determine that?

Answer 24

The limiting reactant is S8

Answer 25

No, the limiting reactant is the reactant that produces less product.

Answer 26

Sorry, it is Zn

Answer 27

Right :-)

Answer 28

So, what is the mass of product using the limiting reactant?

Answer 29

Sorry for wait I had to do something. It is 0.07464 mol ZnS

Answer 30

No worries. That is the moles of product. What is the mass of product?

Answer 31

65.38 g Zn

Answer 32

Hm, that's not what I get. How did you do that?

Answer 33

I got it from the first formula

Answer 34

Hm, let me show you how I would do this step:
0.07464 mol ZnS(97.44 g/1 mol) = ? g ZnS

Answer 35

Ok I get it

Answer 36

:-) So, can you find the percent yield?

Answer 37

Wait 7.27 is the theoretical yield

Answer 38

Yep

Answer 39

so what is the actual yield?

Answer 40

The amount of product given in the problem.

Answer 41

Thank you so much

Answer 42

You're welcome! :-)