Question

Find substance given mass percentage

Answer 1

We are told that substance A is comprised of Oxygen, sulfur and Nickel
40% is Oxygen, 21% is Sulfur, and 38% is Nickel.

Find the chemical formula of the substance.

Answer 2

@dtan5457?

Answer 3

@korosh23

Answer 4

take percentages as masses
and use mole formula
mole =mass / molecular mass

Answer 5

find mole of all the three given atoms

Answer 6

make sure all moles that u got are full numbers
or at least close to full
if mole = 1.1 you can round it to 1
if its equal to = 1.9 you can round it to 2
but if its anything in between, you have to multiply all moles to a number that can change decimal in one (or two or three if all have decimals that need to be changed) of your moles to a full number

Answer 7

but not to confuse you
do the first step
find the mole & show it to us what u got
then we'll what we gotta do afterwards

Answer 8

@Somy, i'm really confused. Can you please explain?

Answer 9

Your compound has O, S, Ni
40% is Oxygen
21% is Sulfur
38% is Nickel

now take these percentages as masses
use the formula
mole = mass / molecular mass
I'll do one of the for you and you gotta do the rest
so mole= 40 / 16
mole = 2.5
This is for Oxygen
now do same thing with S and Ni

Answer 10

@Somy, i'm really confused. Can you please explain?

Answer 11

i did explain...
now you gotta do the working

Answer 12

@Somy, I don't understand what you mean by this:
"take percentages as masses
and use mole formula
mole =mass / molecular mass
find mole of all the three given atoms"

I understand what you are trying to say. I just don't know how that solve this equations

Answer 13

So, do I turn 40% to 40g?

Answer 14

i showed you in working of Oxygen
The percentage given - you consider it as mass of the atom
yes

Answer 15

so, 40/16 = 2.5
21/32 = 0.66
38/59=0.64

Now what?

Answer 16

good
now as you need there are no full numbers
multiply all the answers by 2 & show me what you got

Answer 17

@Somy, 5, 1.32, 1.28

Answer 18

no good because we cant round off to full number in this case
now multiply them all by 3 this time

Answer 19

I multiplied them by six. That works fine
\[2.5\times 6=15\]\[0.66\times 6=3.96\]\[0.64\times 6=3.85\]

Answer 20

@Somy

Answer 21

@hartnn @shamim @Somy?

Answer 22

oh very good :) so u can round off 3.96 and 3.85 to 4

Answer 23

Now what. Please help @Somy, @shamim

Answer 24

@Somy?

Answer 25

@Somy, PLEASE, IM begging :(

Answer 26

@Somy ?

Answer 27

;(

Answer 28

im here :D
well now you know that O -15, S- 4 and Ni -4
thus your formula will be
so your compound will have 15 O atoms, 4 S atoms and 4 Ni atoms

Answer 29

And we can simplify that? Cause the answer is NiSO4

Answer 30

@Somy?

Answer 31

hmm wait
i'll calculate myself
coz there is some error

Answer 32

Ok. THANK YOU

Answer 33

What did you get @Somy

Answer 34

this is weird
i mean there is no way i can get 4 O atoms

Answer 35

I am here you have nothing to worry about it anymore

Answer 36

*crickets*

Answer 37

We are told that substance A is comprised of Oxygen, sulfur and Nickel 40% is Oxygen, 21% is Sulfur, and 38% is Nickel. Find the chemical formula of the substance.

where is the other 1%

Answer 38

@dan815, not sure. Let me check again...

Answer 39

40.3, 21.7, 38

Answer 40

That should help, @Somy

Answer 41

@Somy?

Answer 42

@Somy?

Answer 43

im still getting same ratio

Answer 44

Then I am not sure. It definately says thats it

Answer 45

i guess so then

Answer 46

How would we do the same thing with 10.1% Carbon, 40.4% Oxygen and 49.5% Nickel?

Answer 47

Assume we have 10.1g of carbon, divide by 12?

Answer 48

yeah same way

Answer 49

So, wait
\[10.1/12=0.84\]\[40.4/16=2.525\]\[49.5/58.7=0.84\]Now what?

Answer 50

@Somy

Answer 51

multiply by a number that will change them all to a whole number

Answer 52

0.84 * 5 = 4.2
0.84 * 5 = 4.2
2.5 * 5 = 10

Answer 53

seems good enough

Answer 54

Then, we divide everything by 2?

Answer 55

what is the answer that you have for it?

Answer 56

NiCO3

Answer 57

once you have found the moles of each (0.84, 0.84, and 2.5) \(instead\) of multiplying by a random number and hoping to get whole numbers when you're done, \(divide\) each one of those by the smallest of the set to maintain the molar ratio.

Take 0.84 moles C, 0.84 moles Ni, and 2.5 moles O, and divide them all by 0.84

Answer 58

That way you get a molar ratio of Ni:C:O as 1:1:3.005, which easily rounds to 1:1:3

Answer 59

That makes WAY more sense. THANK YOU @JFraser :D

Answer 60

oh goooooooooood i totally forgot this part!
@JFraser thanks a loooot
@Ahsome and im soooo sorry

Answer 61

YW

Answer 62

Its fine @Somy, you helped a bunch too! Is it bad to assume 100g tho?

Answer 63

that's exactly what you should do

Answer 64

you could assume any starting mass, but we use "100g" as the starting amount because it's easy to find 10.1% of 100g

Answer 65

Ahh, K. I would just state that as an assumption?

Answer 66

if you have to explain the process, yes

Answer 67

Ahh, K :)