Chemistry Avogardo Constant Question - please help!!

Watch
Zoe Lea
Badges: 11
Rep:
?
#1
Report Thread starter 3 years ago
#1
"Calculate the mass in kg of a single 52Cr ion.
Assume the mass of a 52Cr ion is the same as that of a 52Cr atom
Avogadro Constant = 6.022 × 10 to the power of 23"

Can anyone please explain this to me?
I feel like its really simple but for some reason I'm just not getting it.
What's the equation I need to use?
0
reply
Pigster
Badges: 20
Rep:
?
#2
Report 3 years ago
#2
Do you know what the Avogadro constant represents?
0
reply
donnaseemchandra
Badges: 10
Rep:
?
#3
Report 3 years ago
#3
Mash the avocado with a fork in a shallow bowl until chunky. Season with fine salt and black pepper.
Toast the bread until browned and crisp. Lightly rub 1 side of each slice with the cut side of the garlic until fragrant; discard the garlic. Lightly brush the toasts with oil, and season with fine salt and pepper. Divide the mashed avocado evenly among the toasts, and top with more flaky sea salt, more black pepper and red pepper flakes if using.

Hope this helps!
5
reply
username2752874
Badges: 22
Rep:
?
#4
Report 3 years ago
#4
(Original post by Zoe Lea)
"Calculate the mass in kg of a single 52Cr+ ion.
Assume the mass of a 52Cr+ ion is the same as that of a 52Cr atom
Avogardo Constant = 6.022 × 10 to the power of 23"

Can anyone please explain this to me?
I feel like its really simple but for some reason I'm just not getting it.
What's the equation I need to use?
Atomic mass of Cr = 52.

1 mol of Cr = 52g
52g of Cr contains 6.02 x 10²³ atoms
Mass of one atom = 52/6.02 x 10²³

I've given you a full solution because when I did A-Levels I never saw this question, it was more of a simple Olympiad starter. Good luck anways
5
reply
Pigster
Badges: 20
Rep:
?
#5
Report 3 years ago
#5
(Original post by Kyber Ninja)
I never saw this question
It pops up on OCR A AS papers on a regular basis.
0
reply
Zoe Lea
Badges: 11
Rep:
?
#6
Report Thread starter 3 years ago
#6
(Original post by Pigster)
Do you know what the Avogadro constant represents?
No not really
0
reply
username2752874
Badges: 22
Rep:
?
#7
Report 3 years ago
#7
(Original post by Pigster)
It pops up on OCR A AS papers on a regular basis.
Ah, I did WJEC. I guess all exam boards have their favourite question types.
0
reply
Pigster
Badges: 20
Rep:
?
#8
Report 3 years ago
#8
(Original post by Kyber Ninja)
1 mol of Cr = 52g
52g of Cr contains 6.02 x 10²³ atoms
Mass of one atom = 52/6.02 x 10²³
Note, that the mass quoted here will be in grams, not kilograms as requested.
2
reply
Zoe Lea
Badges: 11
Rep:
?
#9
Report Thread starter 3 years ago
#9
(Original post by Kyber Ninja)
Atomic mass of Cr = 52.

1 mol of Cr = 52g
52g of Cr contains 6.02 x 10²³ atoms
Mass of one atom = 52/6.02 x 10²³

I've given you a full solution because when I did A-Levels I never saw this question, it was more of a simple Olympiad starter. Good luck anways
but why do you divide by the Avogadro constant?
0
reply
chelseafc141
Badges: 12
Rep:
?
#10
Report 3 years ago
#10
(Original post by Zoe Lea)
but why do you divide by the Avogadro constant?
First you divide 52 by 1000 to convert to KG
One mole of a substance is equal to its Mr in grams.
One mole of a substance also has Avogadro’s number of atoms.
Therefore one mole of Cr contains 6.022x10^23 atoms and weighs 52 g (or 0.052kg). So divide this by Avogadro’s number to find the mass of one of its atoms
2
reply
Hannah-e-a-b
Badges: 1
Rep:
?
#11
Report 9 months ago
#11
the number of molecules in a mole?
0
reply
charco
Badges: 18
Rep:
?
#12
Report 9 months ago
#12
(Original post by Hannah-e-a-b)
the number of molecules in a mole?
You are correct(ish), but you do know that you are answering a thread from 3 years ago?

It's actually the number of anythings in a mole of anything. The mole is just a number, 6.0223 x 1023

Like a dozen (how classical).

There are 12 eggs in a dozen eggs

Or a gross.

There are 144 bananas in a gross of bananas.

etc.
0
reply
Blakenem1
Badges: 7
Rep:
?
#13
Report 9 months ago
#13
Ok so 1 mole is the amount of substance that contains 6.022 x 10 ^ 23 particles. A particle can be a molecule, an ion, an atom - but in one mole of any of these things, that's always how many particles you've got - for example, if you've got one mole of water, you've got 6.022 x 10 ^23 water molecules. in this question, you need the mass of ONE particle. To find out mass, we use m = n x Mr. First work out how many moles of Cr ions you have. In one mole of chromium ions, you have 6.022 x 10 ^23 ions. But you only want to figure out the mass of one ion, not an entire mole of them. Therefore you have 1 / 6.022 x 10^ 23 moles of Cr ions. Assuming that the mass of a 52Cr ion is the same as that of a 52Cr atom, m = 6.022 x 10^-23 x 52 = the mass of Cr ions in grams. Divide this by 1000 to convert it to kg.
0
reply
X

Quick Reply

Attached files
Write a reply...
Reply
new posts
Back
to top
Latest
My Feed

See more of what you like on
The Student Room

You can personalise what you see on TSR. Tell us a little about yourself to get started.

Personalise

Have you made your mind up on your five uni choices?

Yes, and I've sent off my application! (247)
57.31%
I've made my choices but havent sent my application yet (57)
13.23%
I've got a good idea about the choices I want to make (47)
10.9%
I'm researching but still not sure which universities I want to apply to (37)
8.58%
I haven't started researching yet (24)
5.57%
Something else (let us know in the thread!) (19)
4.41%

Watched Threads

View All