Question

HELP!!!
how many moles of aluminum metal would be needed to produce 35.6 grams of Aluminum oxide

Answer 1

in the following synthesis reaction...
4 Al + 3 O2 --> 2 Al2O3

Answer 2

@ParthKohli

Answer 3

@thomaster

Answer 4

step by step please

Answer 5

...ummm

Answer 6

First, how many moles of Al2 O3 is 35.6 grams?

Answer 7

sry, im not good with the moles and stuff....

Answer 8

OK... what is the molar mass of Al2 O3?

Answer 9

101.96g/mol i think

Answer 10

OK. No. of moles of Al2 O3 = mass/molar mass = 35.6/101.96.

Answer 11

ok

Answer 12

then?

Answer 13

All right, now let's review the reaction:

4 Al + 3 O2 --> 2 Al2O3

This reaction means that for every 4 moles of Al, 2 moles of Al2 O3 will be formed. Or, for every 1 mole of Al2 O3, there is 2 moles of Al. Right?

Answer 14

since you balance it out it becomes that (4 Al + 3 O2 --> 2 Al2O3) right?

Answer 15

Yes.

Answer 16

ok then what do i do

Answer 17

after this one, could you help me with another, little bit more difficult, question???

Answer 18

Read the above reply:

This reaction means that for every 4 moles of Al, 2 moles of Al2 O3 will be formed. Or, for every 1 mole of Al2 O3, there is 2 moles of Al. Right?


We know that there are 2.85 moles of Al2 O3. So the number of moles of Al will be double of 2.85 from what we learned.

Answer 19

where did the 2.85 come from

Answer 20

oh, sorry... it's 35.6/101.96.

Answer 21

I mistakenly calculated 101.96/35.6

Answer 22

...?

Answer 23

The number of moles of Al2 O3 is 35.6/101.96 = 0.35 moles.

Answer 24

yes

Answer 25

now, for every one mole of Al2 O3, there's two moles of Al. That means that no. of moles of Al is TWO TIMES no. of moles of Al2 O3.

Answer 26

ok

Answer 27

So what's the double of 0.35? That's the number of moles of Al which the question requires.

Answer 28

0.7?

Answer 29

yes.

Answer 30

ok, then what?

Answer 31

That's all the question requires.

Answer 32

what?

Answer 33

thats the answer?

Answer 34

wow...

Answer 35

The question asks for the number of moles of Aluminium. We've calculated the number of moles of Aluminium.

Answer 36

ok

Answer 37

care to help me with another question?

Answer 38

Unbalanced equation: KClO3 g KCl + O2

Answer 39

How many moles of oxygen gas can be produced when 78.9 grams of potassium chlorate decompose?

Answer 40

i can balance the equation

Answer 41

OK, do so.

Answer 42

soooo...
2KClO3 --> 2KCl + 3O2?

Answer 43

yes, that's right. now - it's given that there are 78.9 grams of potassium chloride. how many moles is that?

Answer 44

ummm

Answer 45

AHHHH

Answer 46

I DONT KNOW!!!

Answer 47

Hint:

no. of moles = given mass/molar mass

Answer 48

uhhhh

Answer 49

78.9...

Answer 50

given mass = 78.9 g
molar mass of KCl = 39 + 35.5 = 74.5

Answer 51

ok...

Answer 52

divide them to get the number of moles.

Answer 53

ok

Answer 54

1.0590...

Answer 55

Well, that's correct. Now notice that the coefficient of oxygen is 3/2 times that of KCl. So the number of moles of oxygen would also be 3/2 times that of KCl.

So what is the number of moles of oxygen then?

Answer 56

1.59?

Answer 57

Seems good! We're supposed to find the mass of oxygen. Now again use the formula given below:

No. of moles = mass/molar mass

The molar mass of oxygen is 32 g. No. of moles is 1.59, as you said. Find its mass.

Answer 58

20.12?

Answer 59

Not quite.

1.59 = mass/32
1.59 * 32 = mass

Answer 60

oh ok

Answer 61

how do you find the molar mass of oxygen...?

Answer 62

The molar mass of O is 16 grams.
The molar mass of O2 is 16 * 2 = 32 grams.

Answer 63

@whpalmer4

Answer 64

@aaronq

Answer 65

Your question hasn't been answered?

Answer 66

yeah, i sorta had to do something else, and didn't get to finish the question...

Answer 67

what is the question, don't really feel like reading through this whole thread.

Answer 68

How many moles of oxygen gas can be produced when 78.9 grams of potassium chlorate decompose? And this is the balanced equation: 2KClO3 --> 2KCl + 3O2

Answer 69

Okay, so convert the mass of potassium chlorate to moles.
--------------------------------------------------------
To convert mass to moles, use the relationship:

\(n=\dfrac{m}{M}\)

where, M=molar mass, m=mass, and n= moles.
--------------------------------------------------

Now use those moles to find the moles of \(O_{2~(g)}\) produced using the stoichiometric coefficients. Set up a ratio using the species of interest, like so:

e.g. for a general reaction:

\(\color{red}{a}A + \color{blue}{b}B\) \(\rightleftharpoons\) \( \color{green}{c}C\)

where upper case are the species (A,B,C), and lower case (a,b,c) are the coefficients ,

\(\dfrac{n_A}{\color{red}{a}}=\dfrac{n_B}{\color{blue}{b}}=\dfrac{n_C}{\color{green}{c}}\)

From here you can isolate what you need.
For example: if you have 2 moles of B, how many moles of C can you produce?

solve algebraically: \(\dfrac{2}{\color{blue}{b}}=\dfrac{n_C}{\color{green}{c}}\rightarrow n_C=\dfrac{2*\color{green}{c}}{\color{blue}{b}}\)

Answer 70

thanks!

Answer 71

no problem !