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Extra Chemistry Stuff > Paper 1 Questions > Flashcards

Paper 1 Questions Flashcards

1
Q

What are the two ways to prepare a buffer?

A
  1. Weak acid and conjugate base salt

2. Weak acid and strong alkali

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2
Q

Equation and colour for [Cr(H2O)₃(OH)₃] with excess OH-

A

[Cr(H2O)₃(OH)₃] -> [Cr(OH)₆]³⁻

green sol to green ppt

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3
Q

What equipment is needed to work out the enthalpy change in a combustion reaction?

A 
Thermometer 
Combustion chamber
Fuel (reactant)
Water 
Stirrer
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4
Q

What are the signs of either side of an electrochemical cell?

A

Left: Negative
Right: Positive

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5
Q

Define electronegativity

A

The relative tendency of an atom in a covalent bond in a molecule to attract electrons in a covalent bond to itself

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6
Q

What is NaClO used for?

A

Bleach

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7
Q

Expression for Kc (the equilibrium constant)

A

Kc= [C]^c x [D]^d/[A]^a x [B]^b

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8
Q

Test for carbonates

A

Add dilute strong acid
Bubble through limewater
If carbonates are present then limewater will turn cloudy

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9
Q

What are the units of each part of the ideal gas equation?

A 
p = pascals
V = m^3
n = moles
R = JK^-1 mol^1 
T = kelvin
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10
Q

What equation is used to find [H+] from [OH-] and Kw?

A

Kw = [H+][OH-]

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11
Q

Equation and colour for reaction of [Cr(H2O)₃(OH)₃] and excess ammonia

A

[Cr(H2O)₃(OH)₃] -> [Cr(NH₃)₆]³⁺

Green ppt to violet sol

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12
Q

In a titration, what goes in the beaker?

A

Alkali and indicator

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13
Q

How does an acidic fuel cell work?

A

At the anode, platinum catalyst splits H2 into protons and electrons.
The polymer electrolyte membrane (PEM) only allows H+ across which forces the e- to travel around the circuit.
This causes an electric current.
At the cathode O2 combines with H+ to form H2O as the only product.

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14
Q

Equation and colour for reaction of [Cr(H2O)₆]³⁺ with zinc and HCl

A

[Cr(H2O)₆]³⁺ -> [Cr(H2O)₆]²⁺

green sol to blue sol

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15
Q

How do you work out the moles or concentration of a product at equilibrium if you know the amount used up of a reactant.

A

Amount produced of a product = amount used up (change in moles) of a reactant.
Make sure to take into account the balancing numbers so that the ratio is 1:1

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16
Q

Equation and colour of reaction of CrO₄²⁻ with acid

A

CrO₄²⁻ -> Cr₂O₇⁻

Yellow to orange sol

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17
Q

Things that effect lattice enthalpy

A

Size of ions (anions and cations)
Charge of ions
Attraction between ions

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18
Q

What is the unit of rate?

A

mol dm-3 s-1

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19
Q

Example:

What is the Ka equation for HNO2?

A

Ka = [H+][NO2-]/[HNO2]

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20
Q

Metal Hydroxide + Acid =

A

Salt and water

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21
Q

Properties of simple covalent molecules

A

Not conductive
Low melting and boiling points
Polar substances will be soluble but non-polar substances won’t be because they can’t form hydrogen bonds with water

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22
Q

Acid + base ionic equation

A

2H+ + O2- -> H2O

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23
Q

Test for ammonium

A

Add a few drops of aqueous NaOH in to the solution and warm
Hold damp litmus paper over the top of test tube
Ammonium will turn litmus paper blue

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24
Q

What is the overall redox equation in a fuel cell?

A

2H2 + O2 -> 2H2O

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25
Q

Which elements form square planar complexes

A

Platinum and Nickel

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26
Q

Name the smaller ligands that form octahedral complexes

A

H2O, NH3, OH-

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27
Q

What are Van der Waals forces?

A

Induced or permanent dipole-dipole interactions

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28
Q

What is the equation for Kp (the gas equilibrium constant)?

A

Kp = p(D)^d x p(E)^e/p(A)^a x p(B)^b

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29
Q

Things to remember when doing titration equations

A
  • The units for volume are dm3 not cm3

- You need to use the molar ratio in the balanced equation to calculate the number of moles

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30
Q

In a titration, what goes in the burette?

A

Acid

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31
Q

Properties of ionic crystal lattices

A

Conductive when molten but not when solid
High melting and boiling points
Mainly soluble in water

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32
Q

Write the equations at the anode and cathode of an acidic hydrogen fuel cell.

A

Anode: H2 -> 2H+ + 2e-
Cathode: (1/2)O2 + 2H+ + 2e- -> H2O

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33
Q

What is another name for induced dipole-dipole interactions?

A

London forces

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34
Q

When the temperature is increased, which direction does equilibrium shift to oppose the change?

A

Endothermic

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35
Q

Colours of 2+ metal aqua complexes with Cl-

A

Cu: blue to yellow sol
Co: pink to blue sol

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36
Q

How to create an Arrhenius plot and find the activation energy and pre-exponential factor

A 
Plot ln(k) against 1/T
Ea= gradient x R
A= e^(y-intercept)
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37
Q

What is the equation for the buffer system in the blood?

A

H2CO3 -> H+ + HCO3-

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38
Q

What is a dipole?

A

A difference in charge between two atoms caused by a shift in electron density in the bond

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39
Q

Properties of giant metallic lattices

A

Malleable
Good conductors
Insoluble except in liquid metals
Melting and boiling points will vary

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40
Q

Equation for enthalpy change of reaction

A

Enthalpy change of reaction = enthalpy of bonds breaking - enthalpy of bond making

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41
Q

In a polar molecule, which element will have a delta negative charge?

A

The element with the highest electronegativity

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42
Q

Test for halides

A

Add nitric acid
Then add AgNO3
If chloride, bromide or iodide is present then a precipitate will be formed
Dissolve in ammonia to determine which halogen

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43
Q

What does adding acid/alkali do to a buffer?

A

Acid:
H+ reacts with A-, equilibrium shifts to the left to restore pH

Alkali:
OH- reacts with H+ to form H2O, equilibrium shifts to the right to restore pH

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44
Q

Equation for acidic buffers

A

HA -> H+ + A-

45
Q

Name the larger ligands that form tetrahedral and square planar complexes

A

Cl-

46
Q

In hydrogen bonding, which element is delta positive

A

Hydrogen

47
Q

Equation and colour for Cu2+ metal aqua complexes with excess NH3

A

[Cu(H2O)₆]²⁺(aq) or [Cu(H2O)₄(OH)₂] -> [Cu(H2O)₂(NH3)₄]²⁺

blue to deep blue sol

48
Q

Oxidation number of oxygen

A

-2
or -1 in peroxide
or varies if in a compound with fluorine

49
Q

Shape and angle of molecule with 6 bond pairs and no lone pairs

A

Tetrahedral 90°

50
Q

How to draw a hydrogen bond

A

Draw a lone pair on the electronegative elements (N, F or O)
Draw a dotted line from the H to the N, F or O
Draw dipoles on the atoms

51
Q

What elements does hydrogen bonding occur between?

A

Hydrogen and fluorine, nitrogen or oxygen

52
Q

Write the equations at the anode and cathode of an alkaline hydrogen fuel cell.

A

Anode: H2 + 2OH- -> 2H2O + 2e-
Cathode: (1/2)O2 + H2O + 2e- -> 2OH-

53
Q

Colours of 2+ metal aqua complexes with little NH3 or OH-

A

Cu: blue to blue ppt
Fe: green to green ppt
Mn: pale pink to brown ppt
Co: pink to blue ppt

54
Q

Shape and angle of molecule with 3 bond pairs and 1 lone pair

A

Trigonal Pyramidal 107°

55
Q

What is the unit of concentration?

A

mol dm-3

56
Q

Metal Oxide + Acid =

A

Salt and water

57
Q

What’s the structure for a Hess cycle

A

Enthalpy change of solution = -lattice enthalpy + enthalpy of hydration of positive ions and enthalpy change of hydration for negative ions

58
Q

What does the value of Kc suggest about the position of equilibrium?

A

Kc < 1, equilibrium moves towards the left (reactants)

Kc > 1, equilibrium moves towards the right (products)

59
Q

What is the equation for measuring enthalpy change and what does each part mean?

A

q=mc(delta)T

q = heat loss or gained (in joules)
m = mass of solution in the insulated container, or mass of water in container (in grams)
c = specific heat capacity of solution or water, 4.18J g^-1 K-1
Delta T = temperature change of solution or water (in K or °C)

60
Q

Describe the dissociation of water

A

It only dissociate a tiny amount, so equilibrium lies well over to the left. Concentration of water is said to be constant.

H2O + H2O -> H3O+ + OH-
H2O -> H+ + OH-

61
Q

Will a metal with a more negative electrode potential be easier or harder to oxidise?

A

Easier

62
Q

How to form an ionic equation

A

Split aqueous elements into ions. Leave liquid, gas and solids. Remove spectator ions. Rewrite.

63
Q

What is the Arrhenius equation?

A

k = Ae^(Ea/RT)
or
ln(k) = -Ea/RT + ln(A)

64
Q

Equation linking water dissociation and concentration of hydroxide and hydrogen ions

A

Kw = [H+][OH-]

65
Q

How to calculate the number of electron pairs in a molecules

A
  • Work out the number of outer shell electrons in the central atom
  • Add the number of atoms bonded to the central atom
  • Add or subtract any oxidation numbers
  • Divide by two.
  • This will give the total number of electron pairs, so subtract the number of bond pairs to find the number of lone pairs.
66
Q

Equation of [H+] from pH

A

[H+] = 10^-pH

67
Q

Which element forms linear complexes

A

Silver

68
Q

Colours for 3+ metal aqua complexes with little OH- or NH3

A

Cr: green to green ppt
Fe: yellow/brown to brown ppt

69
Q

How can hydrogen be stored?

A
  • As a liquid
  • Adsorbed on solid
  • Absorbed in solid
70
Q

What is the average bond enthalpy

A

The energy needed to break one mole of bonds in the gas phase, averaged over many different compounds

71
Q

Shape and angle of molecule with 4 bond pairs and no lone pairs

A

Tetrahedral 109.5°

72
Q

Why is platinum used in a electrochemical cell?

A

It is conductive and inert

73
Q

State one difference between a fuel cell and a conventional electrochemical cell

A
  • fuel cells require a constant supply of fuel

- fuel cells convert energy from a reaction of fuel with oxygen into a voltage

74
Q

How to draw a Hess Cycle for enthalpy of combustion

A

Draw a line from reactants to combustion products (CO2 and H2O) and then write the product and draw two lines to reactants and combustion products
Arrows to/from reactant/combustion products can point up or down depending if the enthalpy change is exo or endothermic
Route 1 is reactants to combustion products
Route 2 is reactants to product to combustion products

75
Q

Shape and angle of molecule with 2 bond pairs and 2 lone pairs

A

Non-linear (Bent) 104.5°

76
Q

Increasing pressure favour which side of the reaction?

A

The side with less moles of gas

77
Q

Equation for calculating rate of reaction

A

Rate of reaction = amount of product formed or reactant used / time

78
Q

How does a homogenous catalyst work?

A

One or more reactants combine with the catalyst to form an intermediate species, which then reacts to form the products and reform the catalyst.

79
Q

How to draw a Hess Cycle for enthalpy of formation

A

Draw a line from reactants to products and then write out the elements and draw two lines to reactants and products
Arrows from reactant/products can point up or down depending if the enthalpy change is exo or endothermic
Route 1 is from reactants to products
Route 2 is reactants to elements to products

80
Q

Acid + Base =

A

Salt and water

81
Q

Halogen colours when dissolved in organic solvent

A

Iodine: violet/pink
Bromine: orange/red
Chlorine: yellow/green

82
Q

What is the assumption for strong acids?

A

[H+] = [HA]

83
Q

Reaction results between halogen and halide compounds

A

The reaction will only occur if the halogen is more reactive than the halide.
Cl2 and KBr (orange solution)
Cl2 and KI (violet solution)
Br2 and KI (violet solution)

84
Q

How to write a complex half equation (when O or H is present)

A

Write out the ionic half equation
Add H+ and H2O to either side to balance the equation
Balance the charges

85
Q

Metal + Acid =

A

Salt + Hydrogen

MASH

86
Q

Equation for Ka

A 
Ka = [H+][A-]/[HA]
Ka = [H+]^2/[HA]
87
Q

General equation for 3+ metal aqua complexes with little OH- or NH3

A

[M(H2O)₆]³⁺(aq) -> [M(H2O)₃(OH)₃] + + 3H₂O or 3NH₄⁺

88
Q

Equation and colour of reaction of Cr₂O₇⁻ with alkali

A

Cr₂O₇⁻ -> CrO₄²⁻

Orange to yellow sol

89
Q

What is the formula for EMF

A

Eøcell = Eø red - Eø oxi

90
Q

General equation for 2+ metal aqua complexes with Cl-

A

[M(H2O)₆]²⁺(aq) -> [MCl₄]²⁻

91
Q

Acid + Carbonate =

A

Salt + CO2 + water

92
Q

What is the equation for pKa?

A

pKa = -log10Ka

93
Q

Are symmetrical molecules polar or non-polar?

A

Non-polar

94
Q

Oxidation number of hydrogen

A

+1

or -1 in metal hydrides

95
Q

When a metal becomes an ion, which orbital loses electrons first?

A

4s

96
Q

Equation and colour for reaction of [Cr(OH)₆]³⁻ complex with H2O2

A

[Cr(OH)₆]³⁻ -> CrO₄²⁻

green sol to yellow sol

97
Q

Equation for half life of a reaction

A

k = ln2/(half life)

98
Q

How to work out the rate constant from a first order rate-concentration graph

A

Calculate gradient

k = gradient

99
Q

Test for sulfates

A

Add a dilute strong acid
Add barium nitrate Ba(NO3)2
If sulfate ions are present then barium sulfate, a white precipitate, will be formed

100
Q

What is the equation for Ka (the acid dissociation constant)?

A

Ka = [H+][A-]/[HA] at start
or
Ka = [H+]^2/[HA]

101
Q

Metal Carbonate + Acid =

A

Salt and Carbon dioxide and Water

102
Q

General equation for 2+ metal aqua complexes with little OH- or NH3

A

[M(H2O)₆]²⁺(aq) -> [M(H2O)₄(OH)₂] + 4H₂O or 4NH₄⁺

103
Q

State a method that is being developed to store hydrogen for possible use in cars

A

As a liquid under pressure

104
Q

What equation is used to show how ammonia acts as an alkali?

A

NH3 + H2O -> NH4+ + OH-

Reversible

105
Q

When the temperature is decreased, which direction does equilibrium shift to oppose the change?

A

Exothermic

106
Q

Equation and colour of reaction of Cr₂O₇⁻ with zinc and HCl or Fe2+

A

Cr₂O₇⁻ -> [Cr(H2O)₆]³⁺

Orange to green sol

107
Q

Properties of giant covalent structures (macromolecular)

A

High melting and boiling points
Insoluble as strong covalent bonds
Graphite/graphene can conduct electricity
Diamond can conduct heat energy

108
Q

The more ionic a bond is, the ……….. the difference in electronegativity

A

Bigger

109
Q

Shape and angle of molecule with 5 bond pairs and no lone pairs

A

Trigonal bipyramidal, 120° and 90°

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