Module 2 Chapter 3

Question 1

What is relative molecular mass (Mr) and relative formula mass?

Answer 1

Weighted mean mass of a molecule/formula unit compared to 1/12th of an atom of carbon-12.

Molecular = covalent
Formula = ionic

Question 2

Avogadro constant

Answer 2

6.02*10^23, or the number of particles in a mole of substance.

Question 3

Amount of substance

Answer 3

Quantity of a chemical substance

Question 4

Explain term ‘mole (mol)’

Answer 4

The SI unit of amount of substance. One mole
contains 6.02*10^23 ‘elementary entities’ (things: particles/ions/atoms/molecules/oranges)

Question 5

Explain term ‘molar mass’

Answer 5

The mass in grams of 1 mole of particles (grams per mol, gmol^-1)

Question 6

How do you figure out molar mass?

Answer 6

Relative formula/molecular mass in grams = 1 mole.

Question 7

Explain the term ‘molar gas volume

Answer 7

The volume occupied by one mole of gas (volume per mole, dm^3mol^-1)

Question 8

Empirical formula

Answer 8

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

Question 9

Molecular formula

Answer 9

Number and type of atoms of each element in a molecule.

Question 10

Calculating empirical/molecular formulae from %mass/mass/Mr

Answer 10

1. Take (%) mass of each element present, and divide by Mr to find moles of each element
2. Simplify ratio by dividing by lowest mole
3. Round/multiply (if ABSOLUTELY necessary) to whole numbers

Question 11

anhydrous crystals

Answer 11

Ionic solid containing no water molecules

Question 12

hydrated crystals

Answer 12

Ionic solid containing water molecules

Question 13

water of crystallisation

Answer 13

Water molecules in an ionic solid

Question 14

Formula of hydrated salt from given percentage/mass composition

Answer 14

1) calculate mass water lost
2) convert residual mass and water mass to moles
3) write as ratio
4) write as whole number ratio

Question 15

Equation involving mass, moles and molar mass?

Answer 15

n = m/M

mass/molar mass = moles

Question 16

Equation involving concentration, moles, and volume?

Answer 16

n = cV

Moles = concentration*volume

Question 17

The Ideal Gas Equation?

Answer 17

pV = nRT

pressurevolume = molesgas constant*temperature

Question 18

Units in the Ideal Gas Equation?

Answer 18

Pressure = Pascals
Volume = m^3
n = mol
Temperature = Kelvin (C+273)

Question 19

What volume is a gas at RTP?

Answer 19

24dm^3

Question 20

What is pressure and temperature at RTP?

Answer 20

Pressure: 101 kPa
Temperature: 293K (20C)

Question 21

Stoichiometry

Answer 21

Ratio of moles in an equation

Question 22

Percentage Yield equation

Answer 22

(actual mass of product /theoretical mass of product)*100

Question 23

Atom economy equation

Answer 23

(Mr desired product(s)/Mr total product(s))*100

Question 24

Benefits for sustainability of developing chemical processes with a high atom economy?

Answer 24

-Lower amounts of reactant needed
-Less energy needed for obtaining raw materials
-Less energy needed for process (less processes for more useful product)
-Less waste products produced/to deal with
-Less energy needed for disposing of waste products

Question 25

What is a Limiting Reagent and how does this factor into equations?

Answer 25

A limiting reagent is the reactant completely consumed in a chemical reaction when reagents are not in stoichiometric amounts - the other reactant is in excess. You should use the limiting reagent for calculations - determine which is limiting using moles and a balanced equation. (If reagent A has x moles, how many moles does reagent B need to have to react fully? )

Question 26

What are two methods to collect gas in experiments?

Answer 26

1) Collecting a gas over water: a bung with a delivery tube is fed into a measuring cylinder held upside down in a water trough 2) Collecting gas in a gas syringe

Question 27

In which situations would you use different methods of collecting gas?

Answer 27

1) collecting gas over water: with large volumes of a gas that doesn’t dissolve in water 2) gas syringe: with smaller volumes of gas