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how many moles in:

. 4g hydrogen molecules 

. 4g hydrogen atoms 

Any1 know how to do this? I would be greatful if you could tell me how to do this aswell thanks guys!! X

Posted: 08-09-12 18:45 by TheComputerGeek

hey: to do this question you need to follow these steps:

we will start from the first one

-First you need a formula for Mole. It would be easier if you use a formula triangle like this one

( since we are working out the mole of H2 molecule, we cover the mole on the triangle (the blue part)

This leaves us with:  Mass (g) / Atomic mass 

Looking back on the question we need to find the Mass of H2 molecule and the Atomic mass of H2 molecule

Mass of H2 molecule given= 4g

Atomic No of H2 molecule....

-H2 is a molecule so this means that you need to find the Atomic no of H atom then times by 2 (since its H2 molecule NOT AN ATOM ON ITS OWN)

Mass of 1 H atom =1 (given in the periodic table)

                                theorfore 1 x 2 = 2

Now plug in the numbers in the formula given 

-Mass (g)/ Atomic mass 

-4g/2 = 2 mol 

therfore in 4g of H2 molecule there is 2 moles of it...

-i guess this is the rusty when it comes to maths in chemistry

For the second question you are working out the ATOMS INVOLVED so you need to find the atomic number of the atoms only

Hope this was useful

Posted: 09-09-12 11:21 by ELectrica!