Q1 Chem Review "Gases"

According to Boyle's Law, the pressure and volume of a gas have _____ relationship.

• an Inverse

• a Direct

Answer explanation

Unlike the direct relationships of volume vs temperature, and pressure vs temperature...

pressure and volume change opposite of each other.

If volume is decreased, pressure is increased.

if volume is increased, pressure is decreased.

The following graph of the direct relationship between volume and temperature suggests that heating a gas (*under constant pressure*) will cause _______ in volume 

• a decrease

• an increase

Answer explanation

a direct relationship (seen on a graph as a straight, upward trending line...)

means that as one variable increases, the other also increases.

and vice versa.

If one decreases, the other decreases too.

In order to convert to Kelvin, you ___ ______ to the Celsius measurement.

(hint... this formula is on the back of your Reference Tables)

• add 100

• add 273

• subtract 273

• divide by 273

• subtract 100

Suppose each balloon in the image is the same volume but contained a different type of gas molecule (H₂ in one balloon, CO₂ in another, and so on...)

What must be true about the number of moles of gas in each balloon?

• They are the same

• The lighter gases have more moles in their balloon

• The heavier gases have more moles in their balloon

Answer explanation

This is called Avogradro's Law.

Equal moles of gases at the same temperature and experiencing the same external pressure will occupy the same volume REGARDLESS of the identity of the gases.

For example...

at STP, 1 mole of any gas occupies 22.4 Liters of volume.

Tags

NGSS.HS-PS1-7

Gases have...

• A definite shape and a definite volume

• A definite shape but no definite volume
• No definite shape but a definite volume
• No definite shape nor volume

Answer explanation

this relates to kinetic molecular theory of gases

gas particles have large amounts of space between them and feel relatively no attractive forces for each other.

gases fill their container entirely and apply pressure to its walls equally.

If I have 5.6 liters of gas in a piston at a pressure of 1.5 atm and compress the gas until it has a new volume is 4.8 L, what will the new pressure inside the piston be?

(assume T₁ and T₂ are the same because it is held constant)

• 1.75 atm
• 1.8 atm
• 1.3 atm
• 1.29 atm

A sample of gas is at 300 K and initial volume of 2.5 L. If the temperature is cooled down to 200 K, what will the new volume be?

(assume P₁ and P₂ are the same because it is held constant.. notice its not mentioned in the problem)

• 1.7 L

• 3.75 L

• 0.6 L

• 24000 L

Consider a sample of oxygen gas at 27.0 °C with a volume of 9.55 L at a pressure of 2.97 atm.  The pressure is changed to 8.25 atm and the gas is heated to 125 °C. 

What’s the new volume? 

• 4.56 L
• 2.59 L

• 15.9 L
• 0.74 L

Answer explanation