Chemistry Class

Question

The molarity of CO2 in Earth’s atmosphere is roughly 0.04 M. How many moles of CO2 can be found in 1.3 x 1012 L of atmosphere?

Answer 1

Hi Jay!

Moles of a solute in a solution can be found by multiplying its concentration (M or mol/L) by its volume.

So the moles of CO₂ can be found like:

moles = MV = 0.04M (1.3 × 10¹² L) = 5.2 × 10¹⁰ mol CO₂

Answer 2

Hello, Jay,

I discovered, late in my career, the absolute importance, and helpfulness, of units. I always ignored the edict "keep the units" in the calculations, but, wow, they were right. When you keep you eye on the pesky things, they help giude in problem solving and also prevent really stupid mistakes. In this case they help guide hoiw we'll solve the problem.

Molarity is defined as moles per liter. Therefore, 0.04 M can also be written as 0.04 moles/1 liter. Hmmm. If we are given the volume of air, in liters, this suggests that if we multiply the two (Molarity x Liters), the liters will cancel, leaving just moles.

(0.04 moles CO²)/(1 liter air))*(1.3x10¹² liters air) =

(0.04 moles CO²)/(1 liter air))*(1.3x10¹² liters air) = (1x10^-2 moles)*(1.3x10¹²) = 1.3x10¹⁰ moles CO₂

And we didn't need a calculator!

Bob