Question

If 4.2 moles of copper metal reacts with 6.3 moles of silver nitrate, how many moles of silver metal can be formed, and how many moles of the excess reactant will be left over when the reaction is complete?

Unbalanced equation: Cu + AgNO3 → Cu(NO3)2 + Ag

Answer 1

2Cu+2AgNO3->Cu(NO3)2+2Ag
Is this correct?

Answer 2

@iPwnBunnies

Answer 3

Almost, take a look at your copper.

Answer 4

What about it? The two would be distributed to both cu and NO which would make 6 which is why I put two different 2s on the opposite side of the equation

Answer 5

On the right? There are 2 moles of nitrate needed in copper (II) nitrate, Cu(NO3)2. The 2 is only for the nitrate. There's one mole of copper that makes Cu(NO3)2.
So there should be 1 mole of copper on the left

Answer 6

No.-. The 2 distributes to everything....

Answer 7

Then, the two should be out front. .-. Then, it'll distribute to everything.
2 CuNO3

Answer 8

But how do you know it goes to the N?

Answer 9

Because the (NO3) was in parentheses, and the 2 came after it. That usually denotes you need 2 moles of that ion for that substance.

Answer 10

Cu+2AgNO3->Cu(NO3)2+2Ag

Answer 11

Ye. c:

Answer 12

Now, you need to use mole ratios to find the limiting reactant, with the silver. Which reactant do you have less of in this reaction, basically.

Answer 13

Wait no, put the 2 in front of the AgNO3 again. :o Was that the one you were talking about?

Answer 14

And the silver.

Answer 15

Ono. I'm confusing now. ._.

Answer 16

Oh my god /).(\

Answer 17

This is the balanced equation:
Cu + 2 AgNO3 --> Cu(NO3)2 + 2 Ag

Answer 18

And then what do I do c:

Answer 19

Use mole ratios to figure out which of the things on the left give you the LEAST amount of silver. That is your limiting reactant, the "ingredient" you have the least of.

Answer 20

.-.

Answer 21

.-.
Otay...We can do that first part. They tell us we have 4.2 moles of copper, Cu.

Can you see from the equation, for every mole of Cu, we can make 2 moles of Ag?

Answer 22

Okay so cu=63.545 ag=69.723 N=14 O=15.999

Answer 23

Nuuu, we don't have to use molar masses here. >.< Just the number of moles.

Answer 24

How do I know those D:

Answer 25

It comes from the given and the balanced equation. ;-;
Cu + 2 AgNO3 --> Cu(NO3)2 + 2 Ag

Answer 26

There's one Cu mole on the left side. On the right, there are 2 Ag moles.
So, for every mole of Cu, we can make 2 moles of Ag.

Answer 27

Earlier on I did this and I use mass :/

Answer 28

Maybe they wanted mass? They just ask about the amount of moles in the problem.

Answer 29

Oh okay

Answer 30

Soooo, we're given 4.2 moles of copper. For every copper mole, we can make 2 moles of silver.
\[(4.2 mol Cu)(\frac{2 mol Ag}{1 mol Cu}) = 8.4 mol Ag\]
This is the amount of moles of silver we expect, if we had "unlimited" AgNO3.

Find the amount of moles you can get from the 6.3 moles of AgNO3 now. :3

Answer 31

Wait wouldn't I cross multiply?

Answer 32

Sorry it took so long my dad had to read though my entire question to make sure I wasn't "cheating"

Answer 33

No. :3 Cross multiplying is just for fractions separated by an equal sign.

Answer 34

LOL

Answer 35

Wait wouldn't it just be 4.2/6.3 cross product 2/1?

Answer 36

Noooo. .-. As I just said, cross multiplying is just for fractions separated by an equal sign. No cross multiplying here.

Answer 37

We're given 6.3 moles of AgNO3. Take a look back at the balanced equation.
Cu + 2 AgNO3 --> Cu(NO3)2 + 2 Ag
For every 2 moles of AgNO3, we make 2 moles of silver. A 1 to 1 ratio.

Answer 38

I thought it was a 1:2 ratio

Answer 39

That was only for the copper.

Answer 40

Cu + AgNO3 → Cu(NO3)2 + Ag

Cu= 4.2 moles
AgNO3= 6.3 moles

you are given two different moles
smallest mole is going to be Limiting reagent
thus amount of other thing will depend on requirement of limiting reagent as well as amount of product will also depend of limiting reagent

thus your smallest mole given is 4.2 mole of Cu
so focus on this mole and find 'mole of AgNO3 - required' for this limiting reagent
formula
\[\frac{ mole~ of~Cu }{ coefficient~of~Cu }= \frac{ mole~of~AgNO_3 }{ coefficient~of~AgNO_3 }\]
you know mole of Cu
and you know coefficients of AgNO3 and Cu
thus find 'required mole of AgNO3'

afterwards
find Excess of AgNO3
Total mole given- required mole = leftover mole of AgNO3


Next
use same formula as above but now instead of AgNO3 you want to find Ag mole
so
\[\frac{ mole~of~Cu }{ coefficient~of~Cu }= \frac{ mole~of~Ag }{ coefficient~of~Ag }\]
you know mole of Cu
u know both coefficients of Cu and Ag from the reaction
thus find mole of Ag

thats it
hope its clear :)

Answer 41

Okay so 6.3mols agno3(2/2)

Answer 42

Yeeeaaahhh. :3 Someh, y u do dis.

Answer 43

lol idk

Answer 44

2/2would equal 1 so the. It totals to 6.3

Answer 45

Ye, you got 6.3 moles of AgNO3. That would yield 6.3 moles of Ag if we can unlimited copper.
So, compare the amount of Ag you get from Cu and AgNO3.

8.4 moles from Cu
6.3 moles of AgNO3.

AgNO3 is our limiting reactant, and only 6.3 moles of silver can be made from this reaction.

Answer 46

S I got the answer :D

Answer 47

Half of it. Now we need to find how much copper will be left over. :3
And Someh sorta wrote that out already. ^.^

Answer 48

wait.....how....how AgNO3 is limiting???

Answer 49

6.3 moles from AgNO3 I mean. And because it yields the least amount of silver. ._.

Answer 50

._.

Answer 51

Cu + 2 AgNO3 --> Cu(NO3)2 + 2 Ag is the balanced equation Someh.

Answer 52

ik

Answer 53

._. AgNO3 is the limiting reactant.

Answer 54

Yeah well I wish she hadn't because I wanted to show me dad hat I can do this

Answer 55

yeah yeah i hear you
im trying to get it ~_~

Answer 56

No I mean he keeps making fun of me and I just wanted to prove I'm worng but now I can't do that .-.

Answer 57

Okie okie. Bring it back. ;3
6.3 moles of silver is the maximum amount of silver we can get out of this reaction, because the AgNO3 limited it.
We need to work backwards to find out how much copper is needed.

Answer 58

.-.

Answer 59

Yeah I'm just gonna get this question wrong now.... I'm crying so just hell with it :c

Answer 60

Noooo don't cry. T_T

Answer 61

You can do this. ^.^

Answer 62

No because I still don't get any of this

Answer 63

._. :l .-. l:
Maybe you should watch a vid on limiting reactant stuffs.

Answer 64

Yeah..... Do I just subtract the original amount of cooper from the calculated one we got ?

Answer 65

Noo. We gotta find the amount of copper needed to make 6.3 moles of silver now.
Remember back, it took 1 mole of Cu to make 2 moles of silver.

\[(6.3 mol Ag)(\frac{1 mol Cu}{2 mol Ag}) = 3.15 mol Cu\]

Answer 66

Now, subtract that from the given amount. That'll give you the amount of copper that's leftover. :3

Here's a vid btw. Khan Academy is gewd at explaining chemistry me thinks.
https://www.youtube.com/watch?v=rESzyhPOJ7I

Answer 67

4.2-3.15=1.05

Answer 68

Ye. c:

Answer 69

Thanks v.v byes...

Answer 70

;-; Take care.