# Help on a question please?Watch

Announcements
Thread starter 8 years ago
#1
3 The human body contains around 0.025 g of iodine molecules, I2. Which of the
following shows the number of iodine atoms in 0.025 g of I2?
The Avogadro constant is 6.02 × 1023 mol–1.
A 0 025
---------
126 9 x. 6 02 1023
.
× . ×
B 0 025
---------
253 8 x. 6 02 1023
.
× . ×
C 253 8
-----------
0 025 x. 6 02 1023
.
× . ×
D 126 9
-------
0 025 x6 02 1023

The answer is A but im not sure why because i thought it was B. i thought it was B because if its Iodine, and its I2, surely you do 126.9 x 2? :| Help.
0
8 years ago
#2
(Original post by EffKayy)
3 The human body contains around 0.025 g of iodine molecules, I2. Which of the
following shows the number of iodine atoms in 0.025 g of I2?
The Avogadro constant is 6.02 × 1023 mol–1.
A 0 025
---------
126 9 x. 6 02 1023
.
× . ×
B 0 025
---------
253 8 x. 6 02 1023
.
× . ×
C 253 8
-----------
0 025 x. 6 02 1023
.
× . ×
D 126 9
-------
0 025 x6 02 1023

The answer is A but im not sure why because i thought it was B. i thought it was B because if its Iodine, and its I2, surely you do 126.9 x 2? :| Help.
yeah, but the question asks you for iodine ATOMS
0
8 years ago
#3
I think you are getting mass and volume mixed up. The number of atoms in 126.9g of iodine is 6.02 x 1023.

The number of atoms in 0.025g is 0.025/126.9 x 6.02 x 1023

Molecular mass is only relevant when its a gas and you are using its volume to determine number of moles or molecular weight.
0
2 years ago
#4
(Original post by Maker)
I think you are getting mass and volume mixed up. The number of atoms in 126.9g of iodine is 6.02 x 1023.

The number of atoms in 0.025g is 0.025/126.9 x 6.02 x 1023

Molecular mass is only relevant when its a gas and you are using its volume to determine number of moles or molecular weight.
sorry but i didnt understand
can u explain this again!
0
2 years ago
#5
Hi!

If you think a bit, you'll realize that the mass of iodine molecules is the same as the mass of iodine atoms. Since they are asking for number of atoms you're answer should be A, i.e. moles of iodine atoms x Avogradro constant.

Hope it helped!
0
2 years ago
#6
Im sure he needed the help 7 years later.....
0
2 years ago
#7
(Original post by theoneandonlybob)
Im sure he needed the help 7 years later.....
LOL just realized this post was 7 years old...
0
X

new posts
Back
to top
Latest
My Feed

### Oops, nobody has postedin the last few hours.

Why not re-start the conversation?

see more

### See more of what you like onThe Student Room

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

### University open days

• Cardiff Metropolitan University
Undergraduate Open Day - Llandaff Campus Undergraduate
Sat, 19 Oct '19
• Coventry University
Sat, 19 Oct '19
• University of Birmingham
Sat, 19 Oct '19

### Poll

Join the discussion

#### Why wouldn't you turn to teachers if you were being bullied?

They might tell my parents (24)
6.86%
They might tell the bully (33)
9.43%
I don't think they'd understand (53)
15.14%
It might lead to more bullying (135)
38.57%
There's nothing they could do (105)
30%