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A Level Chemistry 4 > 2.1 - Atoms and Reactions > Flashcards

2.1 - Atoms and Reactions Flashcards

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1
Q

Describe the structure of an atom including the distribution of mass and charge.

A

Mass of proton: 1. Charge of proton: +1
Mass of neutron: 1. Charge of neutron: 0
Mass of electron: 1/2000th. Charge of electron: -1
Mass is in nucleus (protons and neutrons) with electron cloud surrounding it.

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2
Q

What is the difference between mass (nucleon) number and atomic (proton) number?

A

Mass number - the total number of protons and neutrons in the nucleus of an isotope.
Atomic number - the total number of protons in the nucleus of an atom.

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3
Q

What is an isotope?

A

Atoms of an element (same number of protons) with different numbers of neutrons and different masses.

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4
Q

What does first ionisation energy mean?

A

The amount of energy needed to remove an electron from each atom in 1 mole of gaseous atoms of an element.

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5
Q

What is used as the standard measurement for relative masses?

A

Carbon-12.

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6
Q

Define relative atomic mass (Ar).

A

The weighted average mass of an atom, relative to 1/12th the mass of a carbon-12 atom.
(The weighted average atomic mass of an element, relative to carbon 12, on a scale where carbon 12 is 12.)

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7
Q

Define relative isotopic mass.

A

The mass of an isotope compared to 1/12th the mass of a carbon-12 atom.
(The mass of an isotope of an element, relative to carbon 12, on a scale where carbon 12 is 12.)

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8
Q

How do you calculate the relative atomic mass of an element?

A

Multiply each isotopic mass by the percentage for that isotope, add each of these values together, divide by 100.

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9
Q

Define relative molecular mass (Mr).

A

The mass of one formula unit of a compound relative to 1/12th the mass of a carbon-12 atom.

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10
Q

Predict the ionic charge of groups 1 to 7 in the periodic table.

A 
Group 1 = 1+
Group 2 = 2+
Group 3 = 3+
Group 4 =
Group 5 = 3-
Group 6 = 2-
Group 7 = 1-
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11
Q

Give the formulae of the following compound ions: Nitrate, Carbonate, Sulphate, Ammonium, Hydroxide, Silver and Zinc.

A 
NO3 -
CO3 2-
SO4 2-
NH4 +
OH -
Ag +
Zn 2+
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12
Q

What is the procedure for balancing equations?

A
  1. Write out the atoms involved in each compound.
  2. Check the compound has the correct formula (Balance charges for ionic ones. Check using memory or dot and cross diagrams for covalent ones).
  3. Use big numbers to balance out the number of atoms/ions on each side of the equation.
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13
Q

What does amount of substance mean?

A

A physical quantity. It is the actual number of atoms, ions or molecules present in a substance.

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14
Q

What does the term mole mean?

A

The unit used to measure amount of substance.

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15
Q

What is Avogadro’s constant?

A

The actual number of particles that 1 mole represents - 6.02 x 10 to the 23.

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16
Q

Define the term molar mass.

A

The mass of 1 mole of a substance (mass per mole). Measured in dm3 mol-1.

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17
Q

Define the term molar gas volume.

A

The gas volume of 1 mole of a substance (gas volume per mole). Measured in g mol-1.

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18
Q

What is the empirical formula?

A

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

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19
Q

What is the molecular formula?

A

The actual number of atoms of each element present in a molecule.

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20
Q

What is the procedure for calculating empirical formulae?

A

Divide the mass or percentage given for each element by the molar mass of that element. This produces the number of moles present for each element.
Divide the molar values for each element by the lowest number of moles calculated to give whole numbers.
Multiply up if some numbers are in halves.
Write the empirical formula.

21
Q

How do you work out the mass of something?

A

n x Mr

22
Q

How do you work out the number of particles?

A

n x 6.02 x 10 to the 23

23
Q

How do you work out the volume of gas?

A

n x 24dm3

24
Q

How do you work out the number of moles?

A

c x v

25
Q

What is the ideal gas equation?

A

pV = nRT

26
Q

How do you calculate percentage yield?

A

(Amount actually obtained divided by amount that could have been obtained) x 100

27
Q

Explain the term atom economy.

A

(Molecular mass of the desired products divided by sum of molecular masses of all products) x 100

28
Q

Describe the main advantage of developing chemical processes with high atom economy.

A

Fewer waste materials leading to less environmental pressure. This increases the sustainability of the process.

29
Q

Explain why can a reaction have a high percentage yield but a low atom economy.

A

Percentage yield only looks at the amount obtained for one particular product in a reaction.
Atom economy looks at the ratio of desirable and undesirable products.
Even if you produced the products to a high percentage yield, the atom economy would be low if lots of the products were waste products.

30
Q

What is an acid?

A

A substance that releases H+ ions in aqueous solution.

31
Q

Give the formulae for sulphuric acid, nitric acid, hydrochloric acid and ethanoic acid.

A

H2SO4
HNO3
HCl
CH3COOH

32
Q

Give three types of substance that can be classed as common bases.

A

Metal oxides, metal hydroxides, ammonia.

33
Q

What is a base?

A

A substance that accepts H+ ions in an aqueous solution.

34
Q

What is an alkali?

A

A soluble base that releases OH- ions in aqueous solution.

35
Q

Give the formulae for sodium hydroxide, potassium hydroxide and aqueous ammonia.

A

NaOH
KOH
NH3

36
Q

What is the difference between a strong and a weak acid?

A

Strong acids fully dissociate (ionise) in solution.

Weak acids do not fully dissociate in solution.

37
Q

Describe neutralisation.

A

H+ (aq) + OH- (aq) –> H2O (l)

38
Q

What is a salt?

A

A substance produced when the H+ ion of an acid is replaced by a metal ion or NH4+.

39
Q

Give the general equation for the reaction between an acid and a metal carbonate.

A

Metal carbonate + acid –> salt + water + carbon dioxide

40
Q

Give the general equation for the reaction between an acid and a metal oxide.

A

Metal oxide + acid –> salt and water

41
Q

Give the general equation for the reaction between an acid and an alkali.

A

Alkali + acid –> salt and water

42
Q

Explain the terms anhydrous, hydrated and water of crystallisation.

A

Anhydrous - containing no water or water of crystallisation.
Hydrated - chemically combined with water (the water is incorporated in the structure).
Water of crystallisation - the water that is chemically combined within the structure of a hydrated compound.

43
Q

Give the rules for assigning oxidation numbers to atoms and ions.

A

Always give the oxidation state for an individual ion or atom.
The oxidation state of a free (uncombined) element is always zero.
The sum of the oxidation states in a neutral molecule is zero.
The sum of the oxidation states in an ion equals the charge on the ion.
In either a compound or an ion, the more electronegative element(s) is/are given the negative oxidation state and vice versa.
Fixed oxidation states for atoms/ions in a compound:
Group 1 elements always +1.
Group 2 elements always +2.
Fluorine always -1.
Oxygen always +2 except in F2O when it is +2 and in peroxides when it is -1.
Hydrogen always +1 except in metal hydrides, e.g. NaH when it is -1.
The oxidation state of an element in a monatomic ion is the same as the charge on the ion. E.g. Chlorine in Cl- is -1.

44
Q

What is oxidation?

A

Oxidation is loss of electrons.

45
Q

What is reduction?

A

Reduction is gain of electrons.

46
Q

Give the general trend in oxidation changes for metals and non-metals.

A

Metals tend to form ions by losing electrons to form positive ions. This results in an increase in oxidation number.
Non-metals tend to react by gaining electrons to form negative ions. This results in a decrease in oxidation number.

47
Q

Describe the redox reactions of metals with dilute hydrochloric acid and dilute sulphuric acids. Example: magnesium and dilute hydrochloric acid.

A 
Write the general equation.
Metal + acid --> salt + hydrogen
Write the correct symbols for the reactants and products.
Mg + HCl --> MgCl + H
Use small numbers to balance the charges on ionic compounds and give the correct number of atoms in a covalent compound.
Mg + HCl --> MgCl2 + H2
Balance.
Mg + 2HCl --> MgCl2 + H2
Add state symbols.
Mg(s) + 2HCl(aq) --> MgCl2(aq) + H2(aq)
Add oxidation states.
Mg(s) + 2HCl(aq) --> MgCl2(aq) + H2(aq)
0             +1 -1             +2 -1            0
Write which element has been reduced and the one that has been oxidised.
Magnesium is oxidised: 0 to +2.
Hydrogen is reduced: +1 to 0.
48
Q

Describe how roman numerals give oxidation states.

A

The number gives the oxidation number of the atom or ion in question.
For a metal the number will be given after the metal, e.g. Iron (III) sulphate. This means iron is in an oxidation state of +3.
For a non-metal the number will be given after the compound ion. This will be for a compound with oxygen. As oxygen will be in a state of -2, the roman numeral will always refer to the other non-metal in the compound ion. E.g. Potassium chlorate (V). This means chlorine is in an oxidation state of +5.

A Level Chemistry 4 (12 decks)

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