## rachie19 one year ago Assuming an efficiency of 31.50 % calculate the actual yield of magnesium nitrate formed from 142.4 of magnesium and excess copper (II) nitrate Mg + Cu(NO3)2 = Mg(NO3)2 +Cu

1. rachie19

@Rushwr

2. Rushwr

Do u know how to get this ?

3. Rushwr

Efficiency = actual yield/ theoretical yield *100%

4. Rushwr

First we will have to find the theoretical yield first !

5. rachie19

yh i got 5.841217606g for my actual yiel

6. Rushwr

oh let me check

7. rachie19

but im stuck

8. Rushwr

where are u sucked?

9. rachie19

im not sure what to do next, im trying to find the theoretical yield

10. rachie19

i mean actual

11. rachie19

the one i did was the theoretical i wrote actual

12. Rushwr

oh still wrong ! Wait. I'll tell u .

13. rachie19

ok thanks

14. Rushwr

First u have to find a relationship between Mg and Mg(NO3)2 ! Cuz the information we know is about Mg right?

15. Photon336

$$\color{blue}{\text{Originally Posted by}}$$ @Rushwr First we will have to find the theoretical yield first ! $$\color{blue}{\text{End of Quote}}$$ $\frac{ actual }{ theoretical}*100 = percent, yield$

16. rachie19

to get the theoretical yield. i divided the grams which was given.... 142.4/ 24.31 (1mol (NO3)2/ 1mol of Mg

17. rachie19

i then multiplied by 148.31 g/mol

18. Rushwr

As we can see in the equation the stoichiometric coefficients are 1:1 in Mg:Mg(NO3)3 That means 1 mole of Mg will form Mg(NO3)2 So the next we are doing is finding the moles of Mg present. we know moles = mass divided by molar mass $n _{Mg} = \frac{ 142.4g }{ 24gmol ^{-1} }$ Now we are gonna write the same equation for Mg(NO3)2 But here we don't know the mass, so we take the unknown mass as "x" $n _{Mg(NO3)_{2}} = \frac{ Xg }{ 148.3gmol ^{-1} }$ As I told u earlier moles of Mg = moles of Mg(NO3)2 So we can equalize those 2 equation and find the theoretical mass of Mg(NO3)2 formed. $\frac{ 142.4 g}{ 24gmol ^{-1} } = \frac{ X g}{ 148.3gmol ^{-1} }$ $X= 880g$ Now this is the theoretical mass, but we have to find the actual yield . $efficiency = \frac{ actual yield }{ Theoretical yield } * 100%$ $actual yield = \frac{ Efficiency* theoretical yield }{ 100 }$ $Actual yield = \frac{ 31.5 * 880 }{ 100} = 277.2g$ This is the answer I got. U better check my calculations. Others seems okai

19. Rushwr

I hope u got it @rachie19 :)

20. rachie19

ok i understand what i did wrong. Thank you so much :)

21. Rushwr

Ur welcome !!! And no problem !