Avogadro’s Law

What is Avogadro’s Law Avogadro’s Principle – equal volumes of gases at the same temperature and pressure contain equal numbers of particles

This is a direct relationship! Avogadro’s Formula * n represents the amount of gas V1= V2 n1 n2 This is a direct relationship! So if the amount of gas increases, then the volume will ___________. If the amount of gas decreases, then the volume will __________. increase decrease

Graph for Avogadro’s Law What Laws have we learned were also direct relationships, in which their graphs were similar to Avogadro’s?

**Conversion Factor: 1 mol (any gas) = 22.4 L at STP ** Avogadro’s Law Molar Volume – for a gas is the volume that one mole of that gas occupies at STP Avogadro showed experimentally that 1 mole of any gas will occupy a volume of 22.4L at STP **Conversion Factor: 1 mol (any gas) = 22.4 L at STP **

Avogadro’s Law: Example 1 Calculate the volume that 0.881 moles of oxygen gas at STP will occupy.

Avogadro’s Law: Example 1 Answer Formula: V1 = V2 n1 n2 Remember, at STP: 22.4 L/mol V1 = ? L n1 = 0.881 mol O2 V2 = 22.4 L n2 = 1 mol O2 V1 = 22.4 L .881 mol O2 1 mol O2 After cross multiplying you end up with V1(1 mol O2) = (22.4 L)(.881 mol O2) 1 mol O2 1 mol O2 V1 = ___________ ---------- ---------- ----------- ---------- 19.7 L

Avogadro’s Law: Example 2 How many grams of N2 will be contained in a 2.0 L flask at STP? (Remember- one mole WEIGHS the formula mass in grams)

Avogadro’s Law: Example 2 Answer Remember, at STP: 22.4 L/mol V1 = 2.0 L n1 = ? g N2 V2 = 22.4 L n2 = 1 mol N2 Formula: V1 = V2 n1 n2 First , solve for the number of moles of N2: 2 L N2 | 1 mol N2 = .089 mol N2 | 22.4 L N2 Then, use dimensional analysis to convert from moles of N2 to grams of N2: .089 mol N2 | 28.014 g N2 = | 1 mol N2\ 2.5 g N2