quick CHEM QUESTION!! (1 Viewer)

[syera]

i dont understand... i tried working it out, but i dont get the rite answer... i know the n = m/M thing, but how do i use that for this question?

ive been trying this question all day... why cant i get itt!
it seems so complicated... i dont get it
please help asap...

 

[lourai*87]

Did you look at my diagram?

"CaCO3 --> CaO + CO2

and related to that question, what mass in grams of calcium oxide is produced from 50g of calcium carbonate?"

the mole ratio is 1:1:1 (you understand that yes?) Ok, so going from the diagram, we have

Grams A (thats the CaCO₃) = 50 g.. and we cant go straight to grams B. So now we have to work out the how many moles of CaCO₃ in 50 grams. Thats where the formula comes in. n=m/M

n = 50/100.09 (sum mole weights of Ca = 40.08, C= 12.01 and 3xO =16)
n = 0.4996....

now we have moles A. Since the mole ratio of CaCO₃:CaO is 1:1, then moles B is also 0.4996...

to get back to grams B, we have to use that formula again.
n = m/M
0.4996... = m/56.08 (sum mole weights of Ca = 40.08, O = 16)
m = 0.4996 x 56.08
m = 28.02 g

So, approx 28.02 grams produced. Not exact cos i rounded the .4996 off early. And i presume you understand how to get the mole weight of a substance -- it is just the weights for the elements on the periodic table.

Tell me if that does or doesnt all make sense to you. If its the wrong answer its most likely a calculation error... that is the method you should use. If its hard to follow i will write my working and upload it for you later. Ill be away this weekend so i hope you dont need any more urgent help =p

 

[rbzoid]

hey guys,
i was studying for my chemistry yearly exam, when i came across this question...

the potassium ion has the same configuration as:
a) the sodium ion
b) the neon atom
c) the magnesium atom
d) the sulfide ion

the answer is d) sulfide ion.
but i don't understand how to get that answer...

can anyone explain please?

actually its
e) XTC ion

 

[syera]

Did you look at my diagram?

"CaCO3 --> CaO + CO2
and related to that question, what mass in grams of calcium oxide is produced from 50g of calcium carbonate?"
the mole ratio is 1:1:1 (you understand that yes?) Ok, so going from the diagram, we have
Grams A (thats the CaCO₃) = 50 g.. and we cant go straight to grams B. So now we have to work out the how many moles of CaCO₃ in 50 grams. Thats where the formula comes in. n=m/M
n = 50/100.09 (sum mole weights of Ca = 40.08, C= 12.01 and 3xO =16)
n = 0.4996....
now we have moles A. Since the mole ratio of CaCO₃:CaO is 1:1, then moles B is also 0.4996...
to get back to grams B, we have to use that formula again.
n = m/M
0.4996... = m/56.08 (sum mole weights of Ca = 40.08, O = 16)
m = 0.4996 x 56.08
m = 28.02 g

So, approx 28.02 grams produced. Not exact cos i rounded the .4996 off early. And i presume you understand how to get the mole weight of a substance -- it is just the weights for the elements on the periodic table.

Tell me if that does or doesnt all make sense to you. If its the wrong answer its most likely a calculation error... that is the method you should use.

yes i did look at ur diagram - and yep that all makes sense... i got 28 when i did it aswell, except i thought i was doing it wrong, coz the answer sheet said 22, and im pretty sure its not a calculation error if we both got 28 and i did it a couple of times... i just thought i was doing it wrong - but i guess not!! the answer sheet must be wrong. thanx i always forget all these mole things, so i follow examples while i do the questions. but i cant do that in exams

If its hard to follow i will write my working and upload it for you later. Ill be away this weekend so i hope you dont need any more urgent help =p

lol i think u have helped me more than enough! THANKSS.. enjoy ur weekend