Chapter 3

Question 1

What is the relative molecular mass?

Answer 1

Is the weighted mean mass for one molecule of a substance relative to 1/12 of the mass of a carbon-12.

Question 2

Give an example for relative molecular mass for glucose?

Answer 2

C6H12O6

Question 3

Is relative formula mass the same as relative molecular mass?

Answer 3

Yes

Question 4

What is the amount of substance?

Answer 4

It is the number of particles in a substance in a mole.

Question 5

What is Avogadro substance?

Answer 5

It is the number of particles contained in 12g of carbon-12- 6.02 x 10 to power of 23

Question 6

What is the molar mass?

Answer 6

The mass, in grams, of 1 mole of atoms of an element is equal to its relative atomic mass.

Question 7

What is the molar gas volume?

Answer 7

Is the volume of 1 mole of gas given at a temperature and pressure.

Question 8

What are the standard conditions?

Answer 8

25 degrees and 1 ATM

Question 9

What is the equation for mass using molar mass and moles?

Answer 9

Moles (n) = mass(g) /molar mass (Mr)

Question 10

What is an empirical formula?

Answer 10

Shows the simplest whole-number ratio of atoms in a compound.

Question 11

Example of empirical formula for glucose?

Answer 11

CH2O

Question 12

What is molecular formula?

Answer 12

Is the number of atoms of each element in a molecule.

Question 13

Example of molecular formula for glucose?

Answer 13

C6H12O6

Question 14

What are the steps to determine formula for hydrated salts?

Answer 14

• Mole of anhydrous salt - mass of salt/ Mr of salt
• Mole of water removed with heating - mass of water removed/ Mr of water (18)
• Ratio of water to salt

Question 15

What is an anhydrous compound?

Answer 15

Is one that contains no water molecules

Question 16

What is hydrated mean?

Answer 16

When water is part of the crystalline structure of a substance

Question 17

What does water of crystalline mean?

Answer 17

The water that is part of the solid salt crystal.

Question 18

How to work out chemical formulae?

Answer 18

• mass (g)
• molar mass
• no of moles - mass/molar mass
• Ratio of elements
• Simplest whole ratio

Question 19

What is the equation for gas volume, involving amount of substance?
What happens when volume is in dm3?
What happens when volume is in cm3?

Answer 19

amount= volume/ molar gas volume

n(dm3)/ 24
n(cm3)/24000

Question 20

What is the equation for substance, involving gas volume?

Answer 20

PV=NRT

Question 21

What is the units for PV=NRT?

Answer 21

P- pressure (pa)
V-volume (m3)
N- moles (mol)
R- gas constant (8.315)
T- temperature (K)

Question 22

How to convert cm3 to m3?

Answer 22

x10 to power of -6

Question 23

How to convert dm3 to m3?

Answer 23

x10 to power of -3

Question 24

How to convert degrees to kelvin?

Answer 24

+273

Question 25

How to convert Kpa to pa?

Answer 25

x10 to power of -3

Question 26

How to rearrange PV=NRT for V?

Answer 26

V= NRT/P

Question 27

How to rearrange PV=NRT for R?

Answer 27

R= PV/NT

Question 28

What is the equation for the amount of substance, involving solution volume and concentration?
What happens when volume is in cm3?

Answer 28

amount, mol = concentration (moldm-3) x volume (dm3)

c x v(in cm3)/1000

Question 29

What is the equation for percentage yield?

Answer 29

Actual no. of moles of desired product/ theoretical no. of moles of desired product x100

Question 30

What is the equation for atom economy?

Answer 30

Mr of desire product/ sum of reactants x100

Question 31

What are the economies, ethical + environmental benefits of a high atom economy?

Answer 31

• fewer raw materials are needed so it is more sustainable
• chemical waste is minimised
• more efficient
• less money is spent on separation process