Chapters 10 & 11 – Gases, Gas Laws, and Gas Stoichiometry ...

[Pages:14]Unit 11 Packet - Page 1 of 14

Honors Chemistry - Unit 11

Chapters 10 & 11 ? Gases, Gas Laws, and Gas Stoichiometry

Marchand Tues.Marchk-1 Vocabulary Due: Thurs .

Quiz: Tues Marat ,

Test Date:

Bdrwimhfhwm

VOCABULARY:

Cans !

Ideal gas standard atmospheric pressure diffusion effusion

standard temperature STP molar volume

CONSTANTS/FORMULAS: Boyle's law Charles' law Gay-Lussac's law Combined gas law Dalton's law Graham's law Ideal gas law Molar volume Molecular Mass Determination (of a gas)

OBJECTIVES:

? Memorize the values for STP. ? Memorize and be able to apply the gas laws: Boyle's, Charles, Dalton's law of

partial pressure, Combined gas law, Gay-Lussac's, and Graham's.

? Be able to use molar volume of a gas at STP in problems. ? Be able to calculate gas density at STP. ? Memorize and be able to apply the ideal gas law. ? Memorize the gas constant R = .0821 L-atm/mol-K. ? Be able to do problems involving gas stoichiometry (at STP and other

conditions).

Unit 11 BELLWORK SET ? Gases, Gas Laws, and Gas Stoichiometry

Unit 11 Packet - Page 2 of 14

Review: 1. Draw the dot diagram for Bismuth.

2. Draw the Lewis Structure for the following and identify the VSEPR Shape: A. Carbonate ion

B. silicon disulfide

Current Unit Material 3. A sample of diborane gas (B2H6) a substance that bursts into flame when exposed to air, has a pressure of 345 torr at a temperature of ?150C and a volume of 3.48 L. If conditions are changed so that the temperature is 360C and the pressure is 268 torr, what will be the volume of the sample?

4. The density of a gas was measured at 1.30 atm and 470C and found to be 1.95 g/L. Calculate the molar mass of the gas.

5. Mixtures of helium and oxygen are used in scuba diving tanks to help prevent "the bend". For a particular dive, 46 L of O2 at 250C and 1.0 atm and 12 L He at 250C and 1.0 atm were pumped into a tank with a volume of 5.0 L. Calculate the partial pressure of each gas and the total pressure in the tank at 250C. Hint: Label all of the variables and calculate each tank (oxygen and helium) as separate problems!

6. Calculate the volume of oxygen gas at 85 0C and 789 torr, required for the complete combustion of 45 g of octane (C8H18).

Unit 11 - Gas Laws Notes

Gases: 4 measurable quantities:

Unit 11 Packet - Page 3 of 14

Volume 1 ml = 1 cm3

Pressure

Temperature

# of moles

Variables? V

P

T

N

STP? Standard Temp -- 0?C

+273

-273k

stdpressurettaotmmm

;

'\Mr3Kpa **GAS LAWS ? Must be Memorized!!**!

Boyle's law - P1 V1 = P2 V2 (V varies inversely with P) P4Vb Pby

=p # Graph of P vs V? inversely?

Example. If 1.0 L of a gas at 1.2 atm is allowed to expand to 5.0 L, what is the new pressure?

-

-

-

Pz

P.t2e.taaimmP#N@i=R.kl=PoIy.2IP4Ya?utmIPVit,y=1- .0LVz=5r0L

V? You try: A sample of O2 gas has a volume of 150 ml when its pressure is 720 mm Hg, what will

the volume be if the pressure is increased to 750 mm Hg?

?

Be 720mm

RVFPZVZ

TE

Y?IEmohm

hippy

(Answer: 144 ml)

Charles law: V1/T1 = V2/T2

(V varies directly with the Kelvin temperature)

T must be in Kelvin Graph of V vs T? Directly? Why T in K?

VPTT

Vbtb

otunff Example: A helium filled balloon has a volume of 2.75 L at 20.0 0C . The volume of the balloon

.tw#m5ooImmD-='44mD decreases to 2.46 L after it was placed outside on a cold day. What is the outside temperature?

Tz

VFQ .75L

V+?=V=

I - VI

It ?

tkmfz.tk?5K#=262@@z3a3K T,= 20.0+273=29312

Tz

V,

Vz= 2.46L

V ,

#Vsti

You try: A sample of neon occupies a volume of 752 ml at 25 0 C. What volume will the gas

occupy at 50. 0C?

I

T?@2g983k p ?=Vyq k=V?jh=752mDGa3#

(Answer: 815 ml)

-815.1C

Unit 11 Packet - Page 4 of 14

Gay-Lussac's Law: P1/T1 = P2/T2 (P varies directly with Kelvin Temperature)

P? Pb? Like which other law? Charles Law

PTTP

You Try: Before a trip from Raleigh to NY, the pressure in a tire is 1.8 atm at 20 0C. At the end

of the trip the pressure gauge reads 1444 mm Hg. What is the new temperature in the tire?

Y.tcofda?tm#" aDrr@aak3k)1z=?1=4tf4z4Pm?2me?*?Et=l.(g1. a8amtm) (Answer: 309 K (or 36 0C)) Tz= ?

Combined Gas Law: P1V1 = P2V2

T must be in K!!!

T1

T2

3Te0259t2,733=*2498=K2T?82O2t Example: If 282.4 ml of a gas at 25 0C and 1.3 atm is cooled to 20. 0C and 780 mm Hg. What is the new volume?

. 4mL

VE ?

R?=RV= VERVE

ebay2.7tl3?=2w93m12YyDfYY#Tz=1.03atRnTp, TTPzTu

P,=h3atm Remanded PNFEEVQI

350.4C

You try: a 700. ml gas sample at STP is compressed to a volume of 200. ml, and the temperature -

is increased to 30.0 0C. What is the new pressur=e of the gas in kPa?

e- RYyd=R@V=t3KPPNyaT)yGz=0m@D73KB)(o203o?km)DT 2

=3q3h@

(Answer: 394 kPa)

Unit 11 Packet - Page 5 of 14

Dalton's law of Partial Pressures: pressure of each gas in a mixture is called the

partial pressure of that gas. Total Pressure = sum of partial pressures PT = P1 + P2 + P3 .... etc.

Special case: gases collected by water displacement ? see diagram on board!

Use formula

PT = Patm

=

Pg + PH2O

Total atmosphere gas water

Patm from lab or is given: PH2O = Table page 899 Bluebook )

Example: Oxyogen is collected by water displacement. The barometric pressure and

temperature are 84.5 kPa and 20.0 0C. What is the partial pressure of O2?

P?zo@ 20.8C

=

Palm .tt?HoTPozPoz=P- Paatom

=234KR

= 84.51Pa -2.341Pa - 82.21Pa

You try: A gas is collected over water and the atmospheric pressure is 101.1 kPa at 50 C. What

is the partial pressure of the gas?

-

Palm .tl?tzotPg;Pg=Patm-Ptw=1O1.1KPa-12.34KPa=88.7bKPa

(Answer: 88.8 kPa)

Graham's Law

Review: Effusion? Diffusion?

**Rate of effusion and diffusion varies inversely with the mass of the gas.**

= Rate of gas A = Square Root Mass of gas B

Rate of gas B

Mass of gas A

Example: Compare the rates of effusion of Hydrogen and oxygen at STP.

pthan Hzgaseffuses

3.98 xfaster

-

-

rate of Hz

Ito

.fm#Eh=FI=F.84=3.98 02

You try: Compare the rates of effusion of Fluorine and chlorine

(Answer: Fluorine is 1.4 x faster than chlorine)

Examples of

Dalto'ns Law ;

?

D:E:*F "?w??itII?!???? 7dm + 5atm

@ Water Displacement

.eIeII#e:.:IiIt:iiI

gas molecules

Pitzo + Pg = Palm

Unit 11 Packet - Page 6 of 14

Ideal Gas Law Notes

pPa=1Og5atemf d PV=nRT

Depends

on

Mass

of

(amounts.

gas ! !

Must use the following units with the ideal gas law!

P =- atm V = L T = K n = moles

Keywords :

g. mass ,md ,

amount

)

-

-

-

Ra=lwgaasycson! stant 0.0821 L-atm/mol- K (memorize) nlmustconuert

-

Example:

What

is

the

prepssu?re

exerted

by

a

12.0

g

sample

of

Nitrogen

gas

(N2)

in

a

10.0

L

container at 25 0C?

p= ?

+7273

-

.

12=00821 toatmlmokk (0,43mg .(0821

t.mg?d)(2q8k)N=12.0gNzp#=gnhRgI =o.43mo1PV=1n0.0RL Tvelo.0L

F- 25+273=29812

Practice Ideal Gas Law Worksheet: 1 ? 4 (page 12 in packet)

Gas Stoichiometry

p@

a- Molar Volume - 1 mol of any gas at STP has a volume of 22.4 L

f) * 1 mol = conversion factor (only to be used at STP) 22.4 L

Note :2Y4moI ,

canalsobewsed .

1. ! Example:

What

is

the

mass

of

?L

98.0 ml

of

502 sulfur dioxide

at

STPo?r

canusemdarvolume

(work together on board ? copy

into your notes!)

' 1j3L

t.gsoa-98.MY#.&4Xq=O.28gs0z

You try: What is the mass of 1.33 x 104 ml of O2 at STP?

FEFe=F Gas Density: D = ? -

19gOz

At STP : D = Molar mass

-

Molar volume

-

g/mol (PT) 22.4 L/mol

?#=@ L

In-y1.o964 Ex: What is the density of CO2 at STP?

#

Dq= Mdarmasscoz = 44.01?,

The

,

You try: What is the molar mass of a gas with a density of 1.56 g/L ?

D= MY ; 1.56? . T.to#mM=34..9mEo,

Unit 11 Packet - Page 7 of 14

Molecular Mass Determination from Ideal Gas Law: (see derivation on board)

D = PM density = pressure (atm) x molar mass (PT)/ constant x temp (K)

?RT

Examples & practice on ideal gas law worksheet!

Stoichiometry of Gases

Can do L-L conversions (just like mol-mol) with 2 gases and an equation

35L

Oz

Example: Given: C3H8 (g) + 5 O2 (g) ? 3 C. O2 (g) + 4 H2O (l)

How many L of O2 are required to react with 0.35 L of propane?

**You may have to use molar volume!**

0.35LHspI0w-el.75L@7.g **You may have to use the ideal gas law!**

5.0L

Example 2: Given CaCO3 (s) ? CaO (s) + CO2 (g)

How many grams of calcium carbonate must decompose to frnom 5.0 L of CO2 at STP?

wmonwwrsveaume

5.at?#HdH09I3Ij=22.34gCa03J2LiCls2LitqLz

You try: If 10.0 g of lithium chloride decomposes how many liters of Cl2 gas are produced at STP? (write a balanced equation first!)

10.0g

#M*Y*yuf2EE=2.64Lc@

Example 3: How many liters of H2 at 35 oC and 745 mm Hg are need to react completely with

825 g of WO3?

-

-

-

FL WO3(s) + 3H2 (g) ? W(s) + 3H2O (l)

PV=nRT

D7.moIHe825sW03MgygM3Etgg-10.68mdHz@usePVEnnaRTytov-nrpI.io.68molK00o8.2gkahtamdG08Kf.gE-2n5.5ITL.mo1co-65o5gYwkq5.n

You try: How many L of CO at 27 0C and 788 mm Hg can be produced from 65.5 g of carbon?

2C(s)

+

O2(g)

?

2CO(g)

,5yyerF#i45mp0jg8a-fmfTkD

Next: Practice Stoichiometry & Gas Stoichiometry Sheets

-129.072cg

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