Properties Of Gases (chpt. 10)

Question 1

Gas

Answer 1

A gas is any substance that has no well-defined boundaries but diffuses rapidly to fill any container in which it is placed

Question 2

Three states of matter

Answer 2

Solid
Liquid
Gas

Question 3

To convert from °C to K

Answer 3

Add 273

Question 4

stp

Answer 4

Standard temperature and pressure

Question 5

Standard temperature

Answer 5

273 Kelvin
0°C

Question 6

Standard pressure

Answer 6

1 x 10^5 Pa
100 kPa

Question 7

Boyles Law

Answer 7

States that, at constant temperature, the volume of a fixed mass of gas is inversely proportional to its pressure

pV = k

Question 8

Charles Law

Answer 8

States that, at constant pressure, the volume of a fixed mass of gas is directly proportional to its temperature measured on the Kelvin scale

V
— = k
T

Question 9

Combined gas law

Answer 9

By combining boyles law and Charles law
(stp)

P V. P V
——. =. ——
T. T

T = Kelvin
P = P
V = V
i.e if the volume is given in L use 22.4L at stp

Question 10

Gay - Lussac’s Law of combining volumes

Answer 10

States that, in a reaction between gases, the volume of the reacting gases and the volume of any gaseous products are in the ratio of small whole numbers, provided the volumes are measured at the same temperature and pressure

Question 11

Avogadros law

Answer 11

States that equal volumes of gases contain equal numbers of particles under the same conditions of temperature and pressure

Question 12

At stp one mole of gas occupies 22.4 L

Question 13

Assumptions of the kinetic theory

Answer 13

1. Gases are made up of particles that are in CONTINUOUS, RAPID, RANDOM MOTION, colliding with each other and with the walls of the container
2. There are NO attractive/repulsive forces between the particles of the gas
3. The gas particles are so small and widely separated that the TOTAL VOLUME of all the particles is NEGLIGIBLE compared with the space they occupy
4. Collisions between particles are PERFECTLY ELASTIC
5. The average kinetic energy of the particles in a sample of gas is proportional to the temperature measured on the Kelvin scale

Question 14

Limitations of the kinetic theory of gases

Answer 14

1. There ARE forces of attraction/repulsion between the particles of a gas (van der Waals etc)
2. The total volume of the particles of a gas is not negligible

Question 15

Ideal gas

Answer 15

One that obeys all the assumptions of the kinetic theory of gases under all conditions of temperature and pressure

Question 16

Real gases

Answer 16

Differ from ideal gases because
Forces of attraction/repulsion do exist between the particles
The volume of the particles is not negligible

Question 17

PV = nRT

Answer 17

P = kPa x 10^3 = Pa
V = cm3 x 10^-6 = m3
n = no. of moles
R = 8.31 (constant)
T = °C + 273 = K

Question 18

Volatile liquid

Answer 18

One with a low boiling point

Question 19

When are real gases closest to ideal gases

Answer 19

High temperature
Low pressure

Question 20

Experiment - to measure the relative molecular mass of a volatile liquid using a conical flask

Answer 20

Volatile liquid - ACETONE

1. Find the mass of the conical flask with aluminium foil and the rubber band
2. Add 10cm3 of acetone to the flask (volatile liquid)
3. Make a small hole in the aluminium foil
4. Clamp the flask in a large beaker of boiling water and leave for about 8 minutes or until it has vaporised
5. Record the temperature of the water to get the temperature of the vapour
6. Leave the flask to cool then measure the mass again

DIAGRAM