Maths

[free4spirit]

Hey everyone,

 

My name is Anna and i live in Scotland, and am studying an introductory course with the Open University. This is my first time here! Got reccommended the site by a friend, as I have an assignment to do by tomorrow and am stuck on one particular maths question! If anyone has any pointers, or can possibly help explain this to me, it would be hugely appreciated!

Question : ©

One cubic metre (1 m³) of atmosphere at sea level contains 3.80 × 10² ppm of CO₂ and 5.00 × 10³ ppm of water vapour.

If there is a total of 2.6 × 10²⁵ molecules in 1 m³ of air, calculate how many molecules of CO2 and water vapour there are in 1 m³ of air. Give your answers to the appropriate number of significant figures.

 

Any help would be fantastic! Hope youre all well too

Anna

[Blahah]

Well the major hint is that ppm stands for parts per million.

 

So, if you have 3.80 x 10² ppm CO₂ that means for every 10⁶ (1 million) particles, 3.80 x 10² of them are CO₂.

So the fraction of any volume of air which is CO₂ will be [imath]\frac{3.80 \times 10^2}{10^6}[/imath]

 

Then if you want to find out how many molecules of CO₂ are in any volume of air, you multiply the total number of molecules in that volume of air by your fraction.

 

You've been told 1m³ air contains 2.6 x 10²⁵, so to find the number of CO₂ molecules in 1m³ of air you do [imath]\frac{3.80 \times 10^2}{10^6} \times 2.6 \times 10^{25}[/imath]

 

Then you can go through the same procedure for H₂O. Does that make sense?

 

It's a good idea to get your head around these sorts of calculations, you use them a lot in science.

[free4spirit]

Aahh, cheers soo much for that! Really helped me out

The help is greatly appreciated, as we dont go into Uni for lectures...

We have to figure it out ourselves...

 

Cheers again

 

Annax