Honors Chemistry Chapter 14 Note Packet - Part 2 Mr. Seidel

(student edition)

Chapter 14 problems - Part 2: 56, 58, 83, 87

14.3 Ideal Gases

Calculate the volume of 1.00 mole of Hydrogen at 20.0 oC and 1000.0 torr

2 ways

In general, PTV = PTV is used for

PV = nRT is used for a)

b) (solving for grams, moles, molar mass, density, and problems not at STP)

NIB Let’s review reaction stoichiometry. Note: a “stoich” problem can be recognized by the fact that information from one substances is and the problem also involves a substance.

2 H2 (g) + O2(g)  2 H2O (g)

How many L of Oxygen are needed to react with 50.0 L of Hydrogen at STP?

but..... we can skip steps 2 and 4 due to Avagadro’s Principle - “Equal volumes of gases at equal temperatures and equal pressures contain an equal # of molecules.”

Hey! It also works for nonstandard conditions

How many L of Oxygen are needed to react with 50.0 L of Hydrogen at 100.0 torr and 873 K?

Because the conditions are non-STP values, 22.4 L can’t be used. So you could also use PV=nRT and solve for V (assume one mole). That is, if you want to do it the hard way…

Now it’s possible to do all kinds of problems.....

Density of a gas at STP

Find the density of 1 mole of liquid water at 3.98 oC if 1.00 g takes up 1.00 cm3

Find the density of gaseous water at 0.0 oC and 1.00 atm

See… I told you gases were 1/ the density of liquids and solids!

Density of a gas not at STP

Find the density of gaseous water at 546 K and 4.00 atm

Find the molecular weight of a gas

If 18.0 grams of a gas at 380 torr and 546 K occupies 44.8 L, what is the molecular weight of the gas?

Stoichiometry of gases not at STP

For L to L conversions - just use stoichiometry - it doesn’t matter if conditions are STP or not

see previous sections

gram to Liter

Find the number of liters of Oxygen are generated when 50.0 grams of sodium chlorate is decomposed at 0.950 atm and 20.0 oC.

Liter to gram

If 555 L of carbon dioxide are generated by a lawn mower engine on a lovely Sunday afternoon ( 757 torr and 37.0 oC - well it is kind of hot today...), how many grams of octane were consumed?

Really fun problems....

What is the density of the carbon dioxide produced if 1.19 mL of ethyl alcohol ( C2H5OH) is combusted in a 1000.0 mL volumetric flask at 25.0 oC and 101.8 kPa? The density of the alcohol is 0.791 g/mL.

14.3 continued… Deviation From Ideal Behavior

Real gases - don’t behave according to the KTG - why you may ask?

1. Real gases have molecules that

2. Real gases have

Ideal gas - a gas that conforms exactly to the KTG - - gases only behave close to ideally at pressures and temperatures. At temperatures and pressures, gases deviate greatly from ideal behavior.

There is an equation that enables us to account for deviations in behavior - it contains correction factors that are specific for a gas - Van der Walls equation - you’ll see it in two years in AP Chemistry

Some gases are close to ideal - they are and .

are not too bad

are not even close to ideal

The Ideal Gas Law

Let’s derive the ideal gas law...

Volume is proportional to V is proportional to V is proportional to

so.... V is proportional to

so....

Let’s derive the ideal gas law constant...

R =