Ch. 5 Gases Flashcards by Amber Greene

Elements that Exist as GASES at 25degrees Celsius and 1 atmosphere

All rows thru row/ period 7 ends before Cn at Rg

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What is the boiling point of HCN?

26 degrees Celsius

But it is close enough to qualify as a gas at ordinary atmospheric conditions.

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Name some physical characteristics of gases:

-Assume VOLUME & SHAPE of containers
-MOST COMPRESSIBLE state of matter
-Mix EVENLY & COMPLETELY when
confined to the same container
-Much LOWER DENSITIES than liq & solid
-Most are COLORLESS

NO2 gas (Nitrous Oxide)

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What is air made up of ?

N2 78%
O2 21%
&
Trace amounts of CO2, H2O, & Ar

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Pressure of a Gas Unit Conversions

760mm Hg = 760 torr = 1 atm =
1.01x10^5 Pascals

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What is the pressure (in atm) if the barometer reading is 688mm Hg ?

688mm Hg / 760 mm Hg = .905 atm

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Who invented the barometer?

BET - DC=degrees Celsius

Evangelists Torricelli 1643

-filled tube of mercury, inverted it into a dish of mercury
-Mercury rose to 760mm at sea level 0DC
-defined standard atm pressure

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What changes and causes the Hg level to change in a barometer?

Atmospheric Pressure changes-

The weight of the HG in tube is supported by atmospheric pressure; as it changes the Hg level changes

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What is an example of atmospheric pressure in play?

Drinking through a straw creates a vacuum & the liquid rushes into the straw to replace the air that was sucked out- to equalize the pressure.

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What is used to measure the pressure of a gas >= atmospheric pressure?

Open-Tube Manometer -
the difference in h + atm pressure = pressure of the gas
(Open tube bc you let in atm pressure bc it’s greater than or =to it so it must be open)

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What is used to measure pressures of a gas < atm pressure ?

Closed-Tube Manometer

The difference in height, h, of the 2 levels = pressure of the gas

(It needs to be closed to trap the pressure since it’s less than atm pressure)

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Boyle’s Law

B- PIV- Pressure Inverse to volume
BPV (PPT means proportional to)
Pressure PPT 1/Volume

B - PV =K (constant)
Boyle’s - (Pressure)(Volume) = k
k=proportionality constant
P=(1/V)K

Volume at CT is inversely PPT to Pressure

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What is used to study the relationship between Pressure & Volume of a Gas?

The J-Tube

As the pressure of the gas increases the volume decreases
P=1/V (Boyle’s Law)

Pressure = 1/Volume (inverse)

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Who says Pressure PPT 1/V
P*V= k (constant)
P1V1=P2V2

P=1/V at constant temp and amt of gas

Boyle’s Law

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What are some deviations from ideal behavior when considering the ideal Gas law?

Assumptions made by the Ideal Gas Law:
-molecules in a gas do not exert force
-the volume of the molecules is negligible
SOME CONDITIONS where real gases do not act like Ideal gases:
1) changes at high Pressure (>5atm) (attractive or repulsive forces when molecules are close)
2) changes at low Temp (decreases KE, making it hard to break attractions)

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P*V=constant means? And whose law is this?

P1V1=P2V2

Boyle’s Law

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A sample of Chlorine gas occupies a volume of 946 mL at a pressure of 726mm Hg. What is the pressure of the gas (in mm Hg) if the volume is reduced at constant temp to 154mL?

(946mL)*(726mmHg)=(154mL)(?)

(686796)/154=4,459.714

The pressure of the gas is 4460mm Hg

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What is Charle’s Law?

Temp & Volume increase proportionally

Volume of fixed amount of GAS
at Constant Pressure PPT Absolute Temp
(In Kelvin) of as gas

Direct relationship between
Temp & Volume T^V^

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What is the temperature & volume relationship at constant pressure ?

Whose Law is it?

Charles Law - temp increases PPT volume

Pressure represented by the mercury which remains constant
As the gas increases the mercury gets pushed up increasing pressure with volume of gas

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How do you get partial pressure of something when you are giving the moles of 3 things and a total pressure atm?

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You take the moles of the gas you are looking for partial pressure of and divide it by the total of all 3 moles given.

Then you take that total and multiply it by the total pressure atm given and that outcome is your answer in atms

What is Charles’s & Gay-Lussac’s Law?

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CVT - Charles Volume PPT Temp

Volume = (PPTk)*(Temp)
Volume/Temp=a constant number
—this # should remain the same every time a volume and temp are divided
V1/T1=V2/T2

Regardless of the pressure each gas conversed at the same temperature which is?

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-273.15 °C

Lord Kelvin 1848 called this ABSOLUTE ZERO -lowest theoretically attainable temp

0 Kelvins= -273.15 °C

A sample of carbon monoxide Gas occupied 3.20 L at 125°C. At what temperature will the gas occupy a volume of 1.54 L if the pressure remains constant?

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V/T=V/T

125°C + 273.15K = 398.15K

(1.54L)*(398.15K) / (3.20L) =191.61K

Remember to cross multiply then divide with division problems

Avogadro’s Law

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Avogadro includes Moles!

At Constant TP, Volume & Moles change direct PPT to each other

n^V^

V/n=V/n
Volume = change constant * Moles

3H2 + N2 =

2NH3 Avogadro’s Law

Ammonia burns and oxygen to form nitric oxide (NO) and water vapor. How many volumes of NO are obtained from one volume of ammonia at the same temperature and pressure?

2NH3 + 3O2 —> 2NO + 3H2O

Increasing or decreasing a volume of gas at constant temp

Boyle’s changes Volume A pressure increases and pushes down on the volume, the volume decreases Boyle’s Law P=(nRT)*1/V (nRT) is constant

Heating or cooling at gas at constant pressure

Charles’s Law changes temperature V=(nR/p)*T

The volume is dependent on the amount of gas at constant temperature and pressure for which law?

Avogadro’s (Avn) A is V=n(Rt/p)

Ideal Gas Laws

PV=nRT Boyle’s P= 1/V (nRT) Charles V= T*( nR/P) or P= T*(nR/V) Avogadro’s V=n(RT/P)

What is an ideal Gas?

A hypothetical Gas, who is pressure/volume/temperature behavior can be completely accounted for by the ideal gas equation

What are two incorrect assumptions that are made to assume a gas is Ideal?

Molecules do not attract nor repel one another (because they do do this) And the volume of a gas is negligible compared to the volume of its container. (This is false because the volume of a gas is the volume of the container)

What conditions are considered standard temperature and pressure?

0°C and 1 atmosphere

Experiment show that at STP, one mole of an ideal gas occupies how many liters?

22.414 Liters Temp = 0°C + 273.15 =273.15 K Pressure = 1atm PV=nRT then R= PV/nT R= 1(22.414)/1(273.15) = 0.0820574776 Ideal gas constant R= 0.082057 L*atm/mol*K

What is the volume (in liters) occupied by 49.8 g of HCL at STP?

PV=nRT Temp = 273.15k P= 1atm n= 49.8g/36.458gHCL = 1.37 moles HCL V= nRT/p (1.37)(0.082057)(273.15) =30.707 =30.7L

Argon is an inert gas used in lightbulbs to retard the vaporization of the filament. A certain lightbulb containing argon at 1.20 atm and 18°C is heated to 85°C at constant volume. What is the final pressure of argon in the lightbulb (in atm)?

P/T=P/T 1.20/291.15= (?)/(358.15) 1.48atm

What is the Ideal Gas Law for density?

D=PM/RT Project management/route M= moles m=grams

How do you get the molar mass of a gas substance?

M= dRT/P d= density in grams/liter Density*RT/P

A 2.10L vessel contains 4.65 g of a gas at 1.00 ATM and 27.0°C what is the molar mass of the gas?

M=dRT/P D=4.65/2.10 =2.214 273.15+27=300.15 K 2.214(0.082057)(300.15)=54.53 g

What is the volume of CO2 produced at 37°C & 1atm when 5.60g of glucose are used up in the reaction C6H12O6(s) + 6O2(g) -> 6CO2(g)+6H2O(l)

Grams /gram per mol *6 moles produced Gives you moles of CO2 Put the moles into V=nRT/P 4.76L

A sample of natural gas contains 8.24 moles of CH4, 0.421 moles of C2 H6, and 0.116 moles of C3H8. If the total pressure of the gases is 1.37 ATM, what is the partial pressure of propane C3H8?

Divide the moles of propane by the total of all three moles added together. Then take that number and multiply it by the atm given. 0.116/(8.24+0.421+0.116)=0.0132 Ppropane = 0.0132*1.37atm=0.0181atms

Calculate the volume of O2 (in L) required for the complete combustion of 7.64 L of acetylene C2H2 measured at the same Temp & pressure

2C2H2(g)+5O2(g)—> 4CO2(g)+2H2O(l) 5mol O2->2mol C2H2, so 6L O2–>2L O2 7.64L C2H2(5L O2/2LC2H2)=19.2 L O2 (L O2/LC2H2)*7.64L given = L required

Dalton’s law of partial pressures

CONSTANT V&T Ptotal = P1 + P2 The total pressure of a mixture of gases is the sum of the individual pressure that each gas exerts

How to calculate : Mole fraction

Moles of : gas A / (gas A+gas B) Take this fraction *(total pressure) = Partial pressure of the gas Pp=mole fraction *total pressure

What is Van der Waals equation for a non-ideal gas?

(P+an^2/v^2)(v-nb)=nRT For an, just the n=moles is squared, not the a and the v is squared on bottom

Calculate the pressure of 1 mole of CH4 in a 2 L container at 273 kelvins using the Ideal gas law and the Van der Waals equation

When the pressure is constant, the mercury in the tube is constant and gas pushes it up

Density =

Density = PM/RT (Pressure)(g/mol) / (0.821)(tempK)

Example of gas exerting pressure drinking through a straw

Atmospheric pressure pushing down air in the straw, pushing down liquid goes up

Ch. 5 Gases Flashcards

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