3.1.2 Amount of substance

Question 1

What is the ideal gas equation?
(bonus- what are each of them for?)

Answer 1

pV=nRT

p= pressure (Pa)
V= volume (m^3)
n= moles of gas
R= gas constant (8.31 JK^-1 mol^-1)
T= temperature (K)

Question 2

Rearrange the ideal gas equation to make V the subject.

Answer 2

V=nRt/p

Question 3

Rearrange the ideal gas equation to make n the subject.

Answer 3

n=pV/RT

Question 4

The kinetic theory describes the constant motion of gas particles with what assumptions?

Answer 4

1. Gas particles move rapidly and randomly
2. The volume of the actual gas particles is negligible compared to empty space between them.
3. There are no intermolecular attractions or repulsions
4. Collisions between particles are elastic - no energy is lost
5. The average kinetic energy of particles depends only on their temperature.

Question 5

The equation to work out concentration involving mass and volume is:

Answer 5

c=m/V

Question 6

The equation to work out concentration involving moles and volume is:

Answer 6

c=n/V

Question 7

How do you convert cm^3 to dm^3?

Answer 7

divide the volume in cm^3 by 1000

Question 8

How do you convert dm^3 to cm^3?

Answer 8

multiply the volume in dm^3 by 1000

Question 9

How many moles of calcium sulfate are there in 34.05g of CaSO4?

Answer 9

Mr of CaSO4 = 40.1+32.1+(4x16)=136.2
n = 34.05/136.2 =0.2500
0.2500 moles

Question 10

Define molecular formula

Answer 10

The actual number of atoms of each element in a compound.

Question 11

Define empirical formula

Answer 11

The simplest whole number ratio of atoms of each element in a compound

Question 12

Apart from having the same general formula, state 2 other characteristics that the homologous series has.

Answer 12

Any two from:
* show a graduation / trend / gradual change
in physical properties / a specified property
* differ by CH2
* chemically similar or react in the same way
* have the same functional group