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OCR A a-level chemistry > Module 2 - [ch2,3,4] (foundations in chemistry) > Flashcards

Module 2 - [ch2,3,4] (foundations in chemistry) Flashcards

atoms, ions and compounds amount of substance acids and redox

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1
Q

Hydrochloric acid

A

HCl

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2
Q

Sulfuric acid

A

H₂SO₄

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3
Q

Nitric acid

A

HNO₃

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4
Q

ethanoic acid

A

CH₃COOH

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5
Q

bases

A

metal/alkali oxides
metal hydroxides
metal carbonates
ammonia

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6
Q

what makes a chemical a base

A

can neutralise an acid to form a salt
proton acceptor

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7
Q

what is an alkali

A

a base that dissolves in water
group 1 metal hydroxides
in solution they release hydroxide ion (OH~)

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8
Q

gain and loss of oxygen
in terms of hydrogen too

A

gain - oxidation - removal of hydrogen
loss - reduction - gain of hydrogen

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9
Q

what is a redox reaction

A

a reaction in which both oxidation and reduction occurs

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10
Q

what are spectator ions

A

ions that do not change during a reaction

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11
Q

define oxidation in terms of electron transfer and oxidation number

A

loss of electrons
increase in oxidation number

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12
Q

define reduction in terms of electron transfer and oxidation number

A

gain of electrons
decrease in oxidation number

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13
Q

oxidising agent

A

the chemical accepting the electrons
is reduced

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14
Q

reducing agent

A

chemical that is donating the electrons

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15
Q

what do oxidation numbers tell you

A

how electrons are lost or gained in a reaction

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16
Q

what has oxidation number 0

A

pure elements

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17
Q

what is the oxidation number of fluorine

A

-1

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18
Q

what is the oxidation number of oxygen

A

-2

EXCEPT
in peroxides
-1
when reacted with fluorine
+2

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19
Q

why is the oxidation number of oxygen bonded to fluorine +2

A

fluorine is electronegative enough to remove electrons from the oxygen

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20
Q

what is the oxidation number of the halogens

A

-1

can be positive if bonded to oxygen or fluorine

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21
Q

what is the oxidation number of hydrogen

A

+1

EXCEPT in metal hydrides
-1

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22
Q

when an acid is added to water which ion is released into solution

A

H+
(proton)

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23
Q

define acid

A

proton donor

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24
Q

what is a strong acid

A

fully dissociates in aqueous solution
releases all its H+ ions into solution

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25
Q

which base is used to treat acid indigestion

A

magnesium hydroxide
MgOH

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26
Q

what are amphoteric substances

A

substances that can act as acids ands bases

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27
Q

acid + carbonate ->

A

salt, Carbon dioxide , water

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28
Q

what is a salt

A

the product of a reaction in which the H~ ions from the acid are replaced by metal or ammonium ions

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29
Q

metal oxide + acid ->

A

salt , water

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30
Q

acid + alkali ->

A

salt , water

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31
Q

metal + acid ->

A

salt , hydrogen

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32
Q

ammonia(aq) + acid ->

A

ammonium salt

33
Q

what are hydrated crystals

A

crystalline structure containing water

34
Q

what are anhydrous crystals

A

crystalline structure containing no water

35
Q

how is water of crystallisation represented

A

dot formula

36
Q

method to perform a titration

A

use a pipette to measure volume of solution
add indicator
swirl ( use a white tile to clearly see end-point )
add acid into burette
record initial volume
slowly add
record volume leftover in burette when end point has been reached
repeat for concordant results

37
Q

name indicators

A

methyl orange (orange - red)
phenolphthalein pink ( clear - pink )

38
Q

what is the colour of methyl orange as an indicator

A

acid - red
base - yellow
end point - orange

39
Q

how do we indicate an element has more than one stable oxidation number

A

roman numerals

40
Q

what does the avogadro constant represent

A

number of atoms in 12g of carbon-12

41
Q

how can you calculate the mass of 1 mole of an element

A

relative atomic mass in grams

e.g
1 mole of carbon-12 has mass 12g

42
Q

moles {}
give unit too

A

moles = mass/Mr
mol

43
Q

state avogadro’s law

A

under the same temperature and pressure one mole of any gas would occupy the same volume

44
Q

what volume does 1 mole of a gas occupy under room temperature and pressure

A

24 dm^3
24000 cm^3

45
Q

define molar gas volume

A

the volume per mole of gas molecules

46
Q

moles{}
gas

A

moles = volume / 24
(dm^3)

47
Q

what are the ideal ways in which a gas behaves

A

random movement
continuous motion
no intermolecular forces experienced
exert pressure when they collide with each other
no kinetic energy lost in collision
when temp increase, kinetic energies of gases increases

48
Q

ideal gas equation {}

A

pV = nRT
pressurevolume = molesideal gas constant*Temperature
pa * m^3 = mol * Jmol^-1 * K

49
Q

1atm = how many pascals

A

101 kPa

50
Q

converting from degrees to kelvin?

A

+273

51
Q

what does concentration of a solution mean

A

amount of solute dissolved in 1dm^3 of solvent

52
Q

moles{}
conc

A

n = CV
moles = concentration * volume
mol = moldm^-3 * m^3

53
Q

what is a standard solution

A

a solution of known concentration

54
Q

what are the steps to preparing a standard solution

A

weigh the solute
dissolve solute using distilled water
pour solution into a volumetric flask
last traces rinsed and poured in
filled to graduation line
flask inverted to ensure solution is mixed thoroughly

55
Q

concentrated
dilute

A

large amount of solute per dm^3 of solvent
small amount of solute per dm^3 of solvent

56
Q

what is a species in a chemical reaction

A

any particle that takes part in a reaction

57
Q

what does percentage yield mean

A

the efficiency to which reactants become products

58
Q

why is percentage yield never 100%

A

reaction may be at equilibrium
the reactants may be impure
side reactions may occur
reactant or product may be left behind when transferring
loss of products during separation and purification

59
Q

percentage yield{}

A

(actual yield / theoretical yield )* 100

60
Q

what is atom economy

A

the proportion of products which was desired

61
Q

atom economy {}

A

( mrdesired product / mr total products ) * 100

62
Q

Describe what you would see when magnesium reacts with an excess of sulfuric acid [2]

A

Mg/solid dissolves
bubbles (hydrogen gas produced)

63
Q

what is meant by the term mole [1]

A

Amount of substance that has the same number of
particles as there are atoms in 12 g of 12C

64
Q

common use for NaClO [1]

A

bleach disinfectant

65
Q

A student prepares a solution of calcium nitrate by reacting dilute nitric acid, HNO3, with the base calcium hydroxide, Ca(OH)2.

Why is calcium nitrate an example of a salt? [1]

A

The H+ ion in an (nitric) acid has been replaced by a metal ion

66
Q

Explain how the hydroxide ion in aqueous calcium hydroxide acts as a base when it neutralises dilute nitric acid. [1]

A

Accepts a proton OR accepts H+

67
Q

What term is given to the ‘*x H2O’ part of the formula? [1]

A

water of crystallisation

68
Q

Explain what is meant by the term salt [1]

A

when the H+ in an acid is replaced by a metal ion

69
Q

Define an acid. [1]

A

a proton donor

70
Q

Chewing chalk has been used for many years to combat excess stomach acid and indigestion tablets often contain calcium carbonate, CaCO3. Suggest, with the aid of an
equation, how these tablets work. [2]

A

CaCO3 + HCl -> CaCl2 + H20 + CO2
calcium carbonate neutralises the acid

71
Q

Describe and explain the trend, down the group, in the reactivity of the Group 2 elements with water. [5]

A

reactivity increases down the group
atomic radii increases
more electron shielding
nuclear attraction decreases
electron more easily lost

72
Q

Define the term empirical formula. [1]

A

simplest whole number ratio of atoms

73
Q

Using aqueous silver nitrate, it is sometimes difficult to distinguish between chloride, bromide and iodide ions.
How can aqueous ammonia be used to distinguish between these three ions? [3]

A

AgCl dissolves in conc NH3 (aq)
AgBr partially soluble in NH3 (aq)
AgI insoluble in NH3 (aq)

74
Q

Explain what is meant by the term molecular formula. [1]

A

Number AND type of atoms making up a 1
molecule

75
Q

Define the term relative isotopic mass [2]

A

the mass of an isotope relative to 1/12th
the mass of a carbon-12 atom

76
Q

State what is meant by the term isotopes [1]

A

atoms of an element with the same number of protons but different number of neutrons

77
Q

why do isotopes have similar chemical properties [1]

A

same number of electrons in the outer shell

78
Q

Define the term relative atomic mass. [3]

A

weighted mean mass of an atom relative to 1/12th the mass of an atom of carbon-12

79
Q

why would you repeat a titration multiple times

A

for concordant results (within 0.1cm^3 of each other
so you can then reject inaccurate titres

OCR A a-level chemistry (11 decks)

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