Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

GCSE Chemistry > Quantitative chemistry > Flashcards

Quantitative chemistry Flashcards

1
Q

What is meant by the law of conservation of mass?

A

No atoms are lost or made during a chemical reaction so the mass of the products equals the mass of the reactants.

  • This is why chemical reactions are always balanced
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

Information on metal, non-metals, transition metals and the ions they form.

A

Metals form +ions
Non-metals from -ions (apart from H+, hydrogen and NH4+, ammonium)
1 Transition metal can form several +ions (eg Fe2+ and Fe3+)

Note: some non-metal ions exist in compounds, eg Hydroxide ion; OH-

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

True or false an ionic compound has an overall charge?

A

False, in an ionic compound the charges on the ions have to cancel out to leave an overall charge of zero.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

Complete practice questions of working out the formula of ionic compounds

A
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

Why can’t you change the subscripts in a formula?

A

Because it produces a different molecule.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

Complete practice questions on calculating the relative formula mass of a compound

A
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

What is meant by the relative atomic mass, Ar of an element?

A

The average mass of isotopes of that element, weighted to take into account the abundance of each isotope.

^^abundance tells us how common an isotope is

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

What is meant by the relative formula mass of a compound, Mr?

A

The sum of the relative atomic mass of the atoms in the numbers shown in the formula.

INFO
- Relative formula mass = Relative molecular mass = Mr
- Has no units
- Never involves the big numbers (coefficient) UNLESS WHEN CALCULATING ATOM ECONOMY.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

Complete practice questions on calculating percentage by mass of an element in a compound.

A
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

What does the percentage by mass of an element tell us?

A

What percentage of the Mr of a compound is due to one of the elements in a compound.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

Equation to work out percentage by mass of an element in a compound

A

% by mass of an element = (Total Ar of atoms in that element/Mr of compound) x 100

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

The Ar of C = 12, if I take 12g of C, how many moles of C do I have?

A

1 mole, aka 6.02 x 10^23 atoms

this applies to any element

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

How to calculate the number of moles in an atom?

A

Moles = mass of element(g)/Ar of element

Mol = m/Mr

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

Complete practice questions on calculating the moles of an element and a compound

A
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

How to calculate the number of moles in a compound?

A

Moles = mass of compound (in grams)/Mr of compound

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

Complete practice questions on working out the of a number of moles.

A
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

How to calculate the mass of a number of moles, equation:

A

Mass = Moles x Mr

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

Complete practice questions on using moles to balance chemical equations

A
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

Complete practice questions on calculating the number of moles of atoms in one mole of a compound.

A
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

Calcium Hydroxide, Ca(OH)2

calculate the number of moles of atoms in one mole of calcium hydroxide.

A

1 molecule = 5 atoms
1 mole = 5 moles of atoms

^^remember this pattern

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

Complete practice questions on calculating the number of atoms in one mole of a in a compound.

A
22
Q

What is meant by avogrado’s constant?

A

6.02 x 10^23 atoms.

23
Q

Explain why some reactions may appear to involve a change in mass.

A

when a reactant or a product is a gas and its mass has not been taken into account.

24
Q

Complete practice questions on using avogrado’s constant in relation to moles = mass/Mr

A
25
Q

reacting masses practice questions

A
26
Q

What is meant by the limiting reactant of a chemical reaction?

A

The reactant that gets completely used up in a chemical reaction.

The excess reactant is the reactant that doesn’t get completely used up in the reaction.

The limiting reactant is what affects the amount of product formed, ie if we have 0.5 mol of limiting reacting 0.5 mol of product will be produced no matter how much moles we have of the excess reactant.

27
Q

Limiting reactants practice questions

A
28
Q
A
29
Q

What is meant by a solute?

A

A chemical which is dissolved in a substance.

So a solvent is what dissolves the solute.

30
Q

Unit for conc:

A

g/dm^3

31
Q

Concentration =

A

Mass(g)/volume(dm^3)

32
Q

How can we decrease the concentration of a solution?

A

Increase volume of solution and keep mass of solute the same.

33
Q

How can we increase the concentration of a solution?

A

Increase mass of solute and keep volume of solution the same.

34
Q

Why is it impossible to achieve 100% yield in a chemical reaction?

A
  • the reaction may not go to completion because it is reversible
  • some of the product may be lost when it is separated from the
    reaction mixture
  • some of the reactants may react in ways different to the
    expected reaction.
35
Q

Why can percentage yield never be over 100%

A

Because it means atoms would have been created and that is not possible.

36
Q

Formula to calculate the percentage yield of a compound:

A

%yield = (mass of product actually made/ maximum theoretical mass of product)x100

37
Q

Atom economy is aka?

A

Atom utilisation

38
Q

What is atom economy?

A

The measure of starting materials in a reaction that end up as useful products.

39
Q

Why is atom economy important?

A

Environmental importance
- It allows us to increase sustainability by not wasting resources.

Economic importance
- By minimising the production of unwanted products we can save money.

40
Q

Formula to calculate atom economy:

A

(Mr of desired products from equation/Sum of all Mr of all REACTANTS in equation) x 100

  • atom economy cannot be greater than 100% because it would mean atoms are being created - this isn’t possible.
41
Q

How do chemists deal with waste products produced by a reaction?

A
  • To ensure money isn’t wasted, chemists use of by-products by using them in other chemical reactions.
42
Q

Concentration practice questions

A
43
Q

Units of concentration:

A

mol/dm^3 or g/dm^3

44
Q

Equation to calculate the concentration of a solution in mol/dm^3:

A

number of moles(mol)/volume(dm^3)

45
Q

Concentration of a solution; both equations;

A

moles or mass/ volume

46
Q

One mole of a gas occupies a volume of what, at room temperature and pressure?

A

24dm^3

Room temp = 20 deg celc
Room pressure = 1 atmosphere.

47
Q

Volume of a gas equation

A

Volume of a gas = Number of moles x 24

V = 24n

48
Q

V = 24n is the equation for?

A

The volume of a gas

Volume = 24 x number of moles

49
Q

What is meant by the concentration of a solution?

A

the amount of solute there is in a specific volume of the solvent.

50
Q

complete practice questions of volume of gases

A
51
Q

True or false?

The mass of one mole of a substance in grams is numerically equal to its relative formula mass.

A

True, eg

The Ar of C = 12, if I take 12g of C, how many moles of C do I have?

1 mole, aka 6.02 x 10^23 atoms

this applies to any element

52
Q

Understand and use the symbols: =, <, «,&raquo_space;, >, ∝, ~

A

GCSE Chemistry (9 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions