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Chemistry - GCSE > Chemistry: Calculations > Flashcards

Chemistry: Calculations Flashcards

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1
Q

What is relative atomic mass of magnesium?
What is relative atomic mass of oxygen?
What is relative molecular mass of Mgo? (Magnesium oxide

A

Mg - 24
O - 16
Mgo : 40 (16+24)

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2
Q

What symbol is relative atomic mass represented by?

A

(A(littleR))

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3
Q

What symbol is relative formula mass represented by?

A

(M(littleR))

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4
Q

What is relative atomic mass?

A

The mean mass of an atom of an element compared to carbon - 12 (basically just the mass number)

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5
Q

What is relative formula mass?

A

The sum of the relative atomic masses of all the atoms or ions in its formula

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6
Q

What is molecular formula?

A

Molecular formula represents the actual number of atoms of each element in one molecule

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7
Q

What is empirical formula?

A

The simplest ratio of different atoms in a compound

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8
Q

What do you need to know to work out empirical formula?

A

You need to know the mass (g) of each element and Relative atomic mass

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9
Q

What is number of moles equal to?

A

Mass

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10
Q

Ethene has a molecular formula of C(little2)H(little4)

What is the empirical formula?

A

Find highest common factor of two little numbers and divide both by this value
HCF of 2 and 4 is 2
Empirical formula = CH(little2)

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11
Q

Calculate the M(littleR) of Carbon dioxide

A

CO(little2)
=A(littleR) (C) + (2xA(littleR) (O))
=12+(2x16)

M(littleR) of CO(little2) = 44

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12
Q

Calculate the M(littleR) for Ca(NO(little3)(little2)

A

=A(littleR) (Ca) +2 (A(littleR)(N)+(3xA(littleR)(O)))

=40+2(14+(3x16))

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13
Q

What is concentration?

A

The amount of solute dissolved in a stated volume of solution

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14
Q

What are the units for concentration?

A

(gdm^-3)

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15
Q

What is the equation for concentration

A

Concentration = mass of solute / volume of solution

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16
Q

What are the SI units for mass of solute?

A

Grams (g

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17
Q

What are SI units for volume of solution?

A

Decimetre (dm^3)

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18
Q

What is the rule or what happens to mass during a chemical reaction.

A

Mass is not created or destroyed during the course of a chemical reaction

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19
Q

What is the law of conservation of a mass?

A

The mass of reactants must equal the mass of the products in a chemical reaction.

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20
Q

What do we do during a chemical reaction?

A

We rearrange atoms to produce new materials

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21
Q

During a chemical reaction, the mass of the reaction doesn’t change. What is this called?

A

A closed system

22
Q

During a chemical reaction, the mass of the products appears to decrease. What is this called? Why does this happen?

A

Non-enclosed system, gas escaping

23
Q

What happens in a closed system?

A

Mass doesn’t change because no gas is being produced/escaping

24
Q

What happens in a open system?

A

Mass decreases as a gas is being given off

25
Q

2Mg + O(little2) > 2Mgo

I react 10g of magnesium with 5g of oxygen. What mass of magnesium would I form?

A

10g +5g =15g

26
Q

I react 15g of magnesium and form 25g of magnesium oxide. What mass of oxygen reacted?

A

15g +0(little2) =25g

O(little2) =10g

27
Q

In a formula, what do the little numbers do?

E.g.: O(little2) = ?

A

Affect the element behind it

E.g.: O(little2) = o x 2

28
Q

In a formula, what do the big numbers do?

E.g.: 2H(little2)O =?

A

E.g.: 2H(little2)O = 4xH, 2xO

Affect the whole compound

29
Q

In a formula, what do the small numbers outside brackets do?
E.g.: (CO(little3))(little3) =?

A

E.g.: (CO(little3))(little3) =3xc, 9xO

Multiply everything inside the bracket by that number

30
Q

What three things are balance in a chemical equation?

A

Atoms, mass, charge

31
Q

What is the rule for little numbers in a formula?

A

You cannot add or change little numbers, only big

32
Q

What is the easy way of saying what the relative formula mass of a compound is?

A

The relative atomic masses of all elements in compound added together

33
Q

What mass of magnesium oxide is produced when 60g of magnesium is burned in air?

A 
1: get your equation
2Mg + O(little2) > 2MgO
2: get relative atomic masses of:
Mg - 24
O(little2) - 16
MgO - 40
2MgO - 80
2Mg=2x24=48 
2MgO=2x(24+16)=80
3:Learn and apply the following points:
48g of Mg makes 80g of MgO
1g of Mg makes 80/48 = 1.66g of MgO
60g of Mg makes 1.66 x 60= 100g of MgO
34
Q

What is a mole?

A

A way of counting

35
Q

Give Avogadro’s number

A

6.02 x 10^23

36
Q

What does 6.02 x 10^23 represent?

A

1 mole of substance

37
Q

What is the mass of 1 mole of a substance?

A

The relative atomic mass or relative formulaic mass in grams

38
Q

If the relative atomic mass of magnesium is 24, what is the mass of 1 mol of magnesium, and how many atoms does this contain?

A

1 mol of magnesium has a mass of 24g containing 6.02x10^28 atoms

39
Q

What is the equation to calculate the number of moles in any substance?

A

Number of moles of substance= mass of substance (g) / Ar or Mr (use periodic table to find this)

40
Q

What is the mass of 1 mol of carbon atoms?

A

1 x 12 = 1

41
Q

What is 0.1mol of silver dioxide molecules?

A

S= 32
O(little 2) =16 x 2 = 32
32+32 = 64
0.1 mol: 6.4

42
Q

What do moles tend to measure?

A

Particles (atoms or molecules of ions)

43
Q

How many molecules are O(little2)?

A

1 molecule

44
Q

How many molecules is 2MgO?

A

2 molecules

45
Q

What type of equation is 2Mg+O(little2) > 2MgO? What does it tell us in relation to moles?

A

A balanced chemical equation. It shows us that 2 moles of magnesium reacts with 1 mole of oxygen

46
Q

In chemical reactions, what is added in excess? What happens to it?

A

One of the reactants is added in excess and isn’t completely used up in the reaction

47
Q

What is the amount of product in a chemical reaction controlled by? What is this called?

A

The reactant that is not in excess: the limiting reactant

48
Q

What is the ratio of the moles of each substance called?

A

The stoichiometry of the reaction.

49
Q

Calculate the number of molecules in 90g of water

A

Water = H(little2)O
1:calculate relative formula mass of water
Mr(H(little2)O): 1+1+16=18
2:calculate the number of moles in 90g of water
Mole = 90/18 = 5 moles of water
3:multiply the number of moles by Avogadro’s number
5x6.02x10^23=3.01x10^24
^ leave answer in standard form

50
Q

How many atoms/particles/molecules does 1 mole have?

A

6.02x10^23

51
Q

What are the 6 elements that travel in pairs?

A

I(little2), Cl(little2), Br(little2), O(little2), N(little2), H(little2)
Iodine, chlorine, bromine, Oxygen, Nitrogen, Hydrogen

Chemistry - GCSE (9 decks)

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