Atomic structure, analysis and quantitative chemistry Flashcards Preview

GCSE Chemistry C2 > Atomic structure, analysis and quantitative chemistry > Flashcards

Flashcards in Atomic structure, analysis and quantitative chemistry Deck (18)
Loading flashcards...
1
Q

Define mass number

A

The total number of protons and neutrons in an atom

2
Q

Define isotope

A

Atoms of the same element that have different numbers of neutrons but the same number of protons

3
Q

How is the relative atomic mass calculated?

A

An atom’s mass is compared with an atom of carbon-12’s. An average value for the isotopes of the element

4
Q

Define a mole

A

The relative formula mass of a substance, in grams

5
Q

Formula for working out the percentage of an element in a compound

A

mass of element ÷ total mass of compound x 100

6
Q

Define empirical formula

A

The simplest whole number ratio of a compound

7
Q

Working out empirical formulae

A

Percentage to mass (skip if mass given): imagine 100g
Moles: ÷ each mass by its Ar
Simplify ratio: ÷ by smallest number

8
Q

What might cause the yield of a reaction not to be 100%?

A

Reactants may be reversible
Products may be unexpected
Product lost in handling or left in apparatus
Impurity of reactants
More than one product produced so difficult to separate

9
Q

Formula for percentage yield

A

Percentage yield = amount of product produced ÷ maximum amount of product possible x 100%

10
Q

How to work out percentage yield

A

Symbol equation and balance
Mr of reactant(s) and useful product(s)
Relate to reactant(s) mass and find max product
Substitute in formula

11
Q

Why maximise yield and minimise energy waste?

A

Wastes less material and energy

Conserves limited resources and reduces pollution from fossil fuels as energy sources

12
Q

Why might be additives be present in food?

A

To improve taste, appearance or shelf life

13
Q

How do food scientists analyse foods to identify additives?

A

Paper chromatography

14
Q

How might compounds in a mixture be separated and then how can they be identified?

A

Gas chromatography and then mass spectrometry

15
Q

Why is argon often used as a carrier gas in mass spectrometry?

A

It is inert and cheaper than other inert gases

16
Q

Define retention time

A

Time taken for compounds to pass through the mass spectrometry column

17
Q

What makes instrumental analysis useful?

A

It is accurate, sensitive and rapid and is particularly useful when the amount of a sample is very small

18
Q

What does a molecular ion peak show in a mass spectrum?

A

The Mr of the substance