Question

What is the percentage yield of ammonia if 358 g N2 react with excess hydrogen to produce 357 g NH3?

3H2 + N2 2NH3

Answer 1

\[3\text H_2 + \text N_2 = 2\text{NH}_3\]

Answer 2

How many moles is 358 g of N_2 ?

Answer 3

A. 82.1%
B. 60.8%
C. 50.0%
D. 99.7%

Answer 4

I know it's not D

Answer 5

the number of moles \(n\), is equal to the mass \(m\) divided by the molecular mass \(M\)

\[n = m/M\]

Answer 6

do you know the molecular mass of N_2?

Answer 7

no

Answer 8

a periodic table table will tell you the atomic mass of N,
multiply this by two to get the molecular mass of N_2

Answer 9

so the molecular mass of N is 14.01 right?

Answer 10

so when multiplied by two, i get 28.02

Answer 11

good, so how many moles is 358 g of N_2 ?

Answer 12

how do i calculate that?

Answer 13

oh the answer is A right?

Answer 14

\[m= 358 [\text g]\\~\\M= 28.02[\text{g/mol}]\]
\[n = m/M\]

Answer 15

i cannot predict the correct option without the working out

Answer 16

How many moles of N_2 are there?

Answer 17

n=12.77

Answer 18

good

Answer 19

now what?

Answer 20

Now, how many moles is 357 [g] of NH_3?

Answer 21

use \[M_{\text{NH}_3} = M_\text N+3M_\text H\]

Answer 22

\[M_\text N = 14.01\\~\\
M_\text H = 1.01\]

Answer 23

MNH3=17.04

Answer 24

right, so how many moles?

Answer 25

17.04? or is there more to do?

Answer 26

M = 17.04 [g/mol] is the molar mass

there is a mass m = 357 g

how many moles?

n = m/M

Answer 27

n=20.9

Answer 28

careful with rounding
n = 357/17.04
= 20.9507
= 21.0 (3 sig.fig's)

Answer 29

oops. i knew that :') now what?

Answer 30

Let's look at the equation again

\[3\text H_2 + \text N_2 = 2\text{NH}_3\]

We found (above) that 12.77 moles of N_2 were used

How many moles of \(\text{NH}_3\) would we expect if the reaction reached completion?

Answer 31

60 mol?

Answer 32

@UnkleRhaukus

Answer 33

According to the equation, each mole of N_2 should form 2 moles of NH_3, (at completion)

Answer 34

so 12.77 moles of N_2 should form ? moles of NH_3

Answer 35

24.154 moles?

Answer 36

try again 12.77 x 2 =

Answer 37

25.54

Answer 38

yeah, lolz

Answer 39

OK, so we expected 25.54 moles of NH_3 product
but only got 21.0 moles

Answer 40

so the answer is A

Answer 41

82.1%

Answer 42

the percentage yield is
\[Y =\frac{\text{yield}}{\text{expected yield}}\]

Answer 43

right?

Answer 44

yeah about \(82\%\)

Answer 45

Does it all make sense now?

Answer 46

@UnkleRhaukus yeah it does. sorry for taking so long to respond. i had to eat dinner.