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Chemistry > 2.1.3 Amount of substance > Flashcards

2.1.3 Amount of substance Flashcards

1
Q

relative atomic mass definition

A

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

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2
Q

what form will the compound be if asked to calculate the relative formula mass

A

giant ionic

giant covalent

giant metallic

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3
Q

what form will the compound be if asked to calculate the relative molecular mass

A

simple molecular (covalent)

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4
Q

percentage of an element equation

A

no. of atoms of the element x RAM of element
——————————————————————- X100
relative formula mass of compound

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5
Q

definition of molar mass

A

the mass per mole of a substance in g/mol^-1

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6
Q

amount of substance definition

A

chemists use amount of substance as a means of counting the number of particles in a substance. Its unit is the mole (mol)

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7
Q

give Avogadro’s constant

A

6.02 x 10^23

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8
Q

equation for the number of atoms/ions/molecules

A

moles x Avogadro’s constant

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9
Q

equation for number of moles

A

mass
—————–
molar mass

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10
Q

steps for empirical formula calculation

A
  1. find the mass of each element/ compound
  2. calculate moles of each (do not round till the end)
  3. divide the number of moles by the smallest number to get a ratio
  4. adjust the ratio to make the moles whole numbers
  5. you can then write the empirical formula
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11
Q

definition for water of crystallisation

A

water molecules that are bonded into a crystallisation structure of a compound

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12
Q

definition of hydrated

A

a crystallised compound containing water molecules

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13
Q

word equation of the water of crystallisation of hydrated copper sulphate

A

heat
hydrated copper sulphate (blue) —-> anhydrous copper sulphate (white) + water

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14
Q

symbol equation of the water of crystallisation of hydrated copper sulphate

A

CuSO4 . 5H2O —> CuSO4 . 5H2O

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15
Q

definition of anhydrous

A

contains no waters of crystallisation

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16
Q

method for calculating the amount of water in water of crystallisation

A
  1. weigh crucible
  2. add a known amount of hydrated salt
  3. weigh the crucible and hydrated salt together
  4. heat the hydrated salt strongly for a few minutes
  5. weigh and heat the sample until the mass stays constant
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17
Q

what are the assumptions of the water of crystallisation practical

A
  1. assuming all the water has been lost by heating to constant mass
  2. when heat the salt is not breaking down further into other compounds
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18
Q

molar gas volume definition

A

the volume per mole of gas molecules at the stated temperature and pressure (RTP)

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19
Q

what is the standard room temperature and pressure

A

25 degrees celsius

101KPa pressure

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20
Q

moles with dm3 gas volume equation

A

volume (dm3)
——————-
24

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21
Q

moles with cm3 gas volume equation

A

volume cm3
——————
24,000

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22
Q

the ideal gas volume equation

A

pressure x vol = mols x ideal gas constant x temperature

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23
Q

what is temperature measured in the ideal gas equation

A

Kelvin

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24
Q

how do you covert from celsius to kelvin?

A

add 273 to answer

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25
Q

how to covert from KPa to Pa

A

times answer by x10^3

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26
Q

how to covert answer from cm3 to m3

A

x10^-6

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27
Q

how to convert from dm3 to m3

A

x10^-3

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28
Q

what is the method for the ideal gas equation calculation question?

A
  1. convert all units
  2. rearrange equation to workout the unknown
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29
Q

stoichiometry definition

A

the ratio of the amount in moles of each substance in a chemical reaction

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30
Q

steps for stoichiometry calculation

A
  1. state mr for all substances
  2. workout moles for known substance
  3. use ratio to find moles of the unknown
  4. workout the question e.g. vol of gas or mass of substance
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31
Q

steps for limiting reactant calculation

A
  1. workout the moles for both reactants
  2. ratio - how much of each reactant you need
  3. identify the limiting reactant
  4. use the limiting reactants mols to workout the rest of the question
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32
Q

what is concentration measured in?

A

mol dm^-3

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33
Q

moles equation (conc and vol)

A

mols = conc x vol
—————
100

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34
Q

what is volume measured in?

A

cm^3

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35
Q

what is the equation for concentration?

A

mols x 1000
—————-
volume

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36
Q

how do you convert from mol dm^-3 to g dm^-3?

A

times by the Mr

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37
Q

what is the equation for percentage yield?

A

actual moles
———————— X100
theoretical moles

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38
Q

what is the definition of percentage yield?

A

the amount of product made from the starting materials

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39
Q

what are the steps for a percentage yield calculation?

A

1 - workout the Mr of the reactants and products that you have a mass for

2 - workout the actual moles (moles of product)

3 - workout the theoretical moles (moles of the reactant THEN RATIO)

4 - put moles back into equation

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40
Q

what is the equation for atom economy?

A

sum of molar masses of desired
——————————————— X100
sum of molar masses of all products

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41
Q

what is the atom economy if a reaction only has one product?

A

100%

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42
Q

which is the only calculation where you use the big number infront of the element?

A

ATOM ECONOMY

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43
Q

how many kg are in a tonne?

A

1000

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44
Q

what is the definition for empirical formula?

A

the simplest ratio of atoms of each element in a compound

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45
Q

what is the definition of a mole?

A

the amount of any substance containing as many particles as there are carbon atoms in 12g of carbon 12

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46
Q

what is the definition of hydrated?

A

a crystallised compound containing water molecules

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47
Q

what is the definition of Avogadro’s constant?

A

6.02x10^23 the number of carbon atoms in a mole of carbon 12

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48
Q

what is the definition for molecular formula?

A

the actual number of atoms of each element in the compound

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49
Q

What is the definition of a mole?

A

The mole is the amount of substance in grams that has the same number of particles as there are atoms in 12 grams of carbon-12.

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50
Q

Define relative atomic mass.

A

Relative atomic mass is the average mass of one atom compared to one twelfth of the mass of one atom of carbon-12.

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51
Q

What is molar mass?

A

Molar mass is the mass in grams of 1 mole of a substance, given in the unit g mol-1.

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52
Q

How is molar mass calculated for a compound?

A

Molar mass for a compound is calculated by adding up the mass numbers of each element in the compound.

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53
Q

What is the molar gas volume at room temperature and pressure?

A

At room pressure (1 atm) and room temperature (25°C), the molar gas volume is 24 dm³ mol-1.

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54
Q

What is Avogadro’s constant?

A

Avogadro’s constant is 6.02 x 10^23, which indicates the number of atoms in 12 grams of carbon-12.

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55
Q

True or False: 1 mole of any specified entity contains 6.02 x 10^23 of that entity.

A

True.

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56
Q

Calculate the amount in mol for 35.0g of CuSO4 using the formula.

A

0.219 mol.

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57
Q

What is the unit of mass used in amount calculations?

A

Grams.

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58
Q

Fill in the blank: 1000 mg = _______.

A

1 g.

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59
Q

What is the definition of an empirical formula?

A

An empirical formula is the simplest ratio of atoms of each element in the compound.

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60
Q

List the steps to calculate an empirical formula.

A
  • Divide each mass (or % mass) by the atomic mass of the element
  • Divide each of the answers by the smallest one of those numbers
  • Multiply to give whole numbers if needed.
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61
Q

Calculate the empirical formula for a compound with 1.82g of K, 5.93g of I, and 2.24g of O.

62
Q

What is the definition of a molecular formula?

A

A molecular formula is the actual number of atoms of each element in the compound.

63
Q

How do you determine the molecular formula from the empirical formula?

A

From the relative molecular mass (Mr), work out how many times the mass of the empirical formula fits into the Mr.

64
Q

Example: What is the molecular formula for a compound with an empirical formula of C3H6O and a Mr of 116?

65
Q

What is a hydrated salt?

A

A hydrated salt contains water of crystallisation

Example: Cu(NO3)2 - 6H2O is hydrated copper (II) nitrate(V).

66
Q

What is the formula for anhydrous copper (II) nitrate(V)?

A

Cu(NO3)2

Anhydrous means it does not contain water.

67
Q

What is the molar mass of Na2SO4·xH2O if x is 10?

A

322.1 g/mol

Calculation: Molar mass = 180.1 - (23x2 + 32.1 + 16x4).

68
Q

What is the method for measuring mass loss in thermal decomposition reactions?

A

Heating in a crucible

This method measures mass loss or gain during reactions.

69
Q

What happens to the water of crystallisation in calcium sulfate when heated?

A

It is removed as water vapour

Example equation: CaSO4·xH2O(s) → CaSO4(s) + xH2O(g).

70
Q

What is the first step in the method of heating a hydrated salt in a crucible?

A

Weigh an empty clean dry crucible and lid

This ensures accurate measurement of mass loss.

71
Q

What is the significance of using a lid on the crucible during heating?

A

It prevents loss of solid from the crucible

The lid should be loose to allow gas escape.

72
Q

What mass of hydrated calcium sulfate is recommended for accurate results?

A

Use no more than 2g

Large amounts, like 50g, may lead to incomplete decomposition.

73
Q

What is the calculated value of x in ZnSO4·xH2O if 3.51 g of hydrated zinc sulfate yields 1.97 g of anhydrous zinc sulfate?

A

x = 7

Calculation involves determining mass loss and mole ratios.

74
Q

What is a solution in chemistry?

A

A mixture formed when a solute dissolves in a solvent

Water is the most common solvent for aqueous solutions.

75
Q

How is molar concentration calculated?

A

Molar concentration = amount in moles of solute / volume of solution

The unit is mol dm⁻³ or M.

76
Q

What is the unit of volume used in molar concentration calculations?

A

dm³

1 dm³ = 1 litre.

77
Q

Convert 1 m³ to dm³.

A

1 m³ = 1000 dm³

1 m³ is a cube of 100 cm on each side.

78
Q

How do you convert cm³ to dm³?

A

Divide by 1000

1 cm³ = 1 mL.

79
Q

Calculate the concentration of a solution made by dissolving 5.00 g of Na2CO3 in 250 cm³ of water.

A

0.189 mol dm⁻³

Calculation: Conc = 0.0472 mol / 0.25 L.

80
Q

Calculate the concentration of a solution made by dissolving 10 kg of Na2CO3 in 0.50 m³ of water.

A

0.19 mol dm⁻³

Calculation involves converting mass to moles and dividing by volume.

81
Q

What is the formula for mass concentration?

A

mass concentration = mass / volume

82
Q

How do you convert concentration from mol dm³ to g dm³?

A

conc in g dm-3 = conc in mol dm-3 x Mr

83
Q

What is the unit of mass concentration?

84
Q

What happens when soluble ionic solids dissolve in water?

A

They dissociate into separate ions.

85
Q

If 5.86g of sodium chloride (NaCl) is dissolved in 1 dm³ of water, what is the concentration of sodium chloride solution?

A

0.1 mol dm-3

86
Q

What are the concentrations of sodium ions and chloride ions when 0.1 mol of sodium chloride is dissolved?

A
  • Sodium ions: 0.1 mol dm-3
  • Chloride ions: 0.1 mol dm-3
87
Q

What is the concentration of magnesium ions and chloride ions when 9.53g of magnesium chloride (MgCl₂) is dissolved in 1 dm³ of water?

A
  • Magnesium ions: 0.1 mol dm-3
  • Chloride ions: 0.2 mol dm-3
88
Q

What is the first step in making a solution?

A

Weigh the sample bottle containing the required mass of solid on a 2 dp balance.

89
Q

What should be done if the substance does not dissolve well in cold water?

A

Heat the beaker and its contents gently until all the solid has dissolved.

90
Q

How should you ensure a uniform solution after making it?

A

Invert the flask several times.

91
Q

When diluting a solution, what remains constant?

A

The amount of moles of solute present.

92
Q

What is the formula for calculating dilutions?

A

Original volume x original concentration = new diluted volume x new diluted concentration

93
Q

What is the new diluted concentration if 50 cm³ of water is added to 150 cm³ of a 0.20 mol dm-3 NaOH solution?

A

0.15 mol dm-3

94
Q

How much water must be added to dilute 5.00 cm³ of 1.00 mol dm-3 hydrochloric acid to a concentration of 0.050 mol dm-3?

95
Q

What personal protective equipment should be worn when handling dilute acids and alkalis?

A

Wear goggles.

96
Q

True or False: Hazardous substances in low concentrations pose the same risks as the pure substance.

97
Q

What is Avogadro’s Constant?

A

6.02 x 10^23 particles per mole

This constant is used to define the number of atoms, molecules, or ions in one mole of a substance.

98
Q

How many atoms are in 1 mole of copper?

A

6.02 x 10^23 atoms

This is a direct application of Avogadro’s Constant.

99
Q

How do you calculate the number of particles in a substance?

A

Number of particles = amount of substance (in mol) x Avogadro’s constant

This formula is applicable for any specified entity.

100
Q

What is the formula to calculate density?

A

Density = mass/volume

Density is typically expressed in g cm^-3.

101
Q

What is the amount of substance in moles for 6.00 g of tin with Ar = 118.7?

A

0.05055 mol

This is calculated using the formula: amount = mass/Ar.

102
Q

How many chloride ions are produced from 25.0 cm³ of 0.400 mol dm^-3 magnesium chloride?

A

1.204 x 10^22 ions

This calculation involves determining the amount of magnesium chloride and the stoichiometry of the reaction.

103
Q

Fill in the blank: The density of ethanol is ______ g cm^-3.

104
Q

What is the mass of ethanol in 0.500 dm³ of ethanol?

A

394.5 g

This is calculated using the density and volume: mass = density x volume.

105
Q

What is the density of gold calculated in kg dm^-3?

A

19.3 kg dm^-3

This is determined from the mass and volume of the gold bar.

106
Q

True or False: 1 mole of sodium ions contains 6.02 x 10^23 ions.

107
Q

What is the first step in converting quantities between different substances using a balanced equation?

A

Convert any given quantity into amount in mol

This can be done using mass, volume of gas, or concentration.

108
Q

How do you calculate the mass of carbon dioxide produced from heating sodium hydrogencarbonate?

A

mass = amount x Mr

This follows a three-step process involving the balanced equation.

109
Q

What is the total volume of gas produced from the decomposition of 0.651 g of magnesium nitrate?

A

0.303 dm³

This requires calculating moles of magnesium nitrate and applying the ideal gas law.

110
Q

How do you calculate the concentration of H₂SO₄ from a neutralization reaction?

A

Concentration = amount/volume

This is derived from the moles of H₂SO₄ obtained from the balanced equation.

111
Q

What is the mass of copper that reacts with 150 cm³ of 1.60 mol dm^-3 nitric acid?

A

5.71 g

This is determined through a series of calculations involving stoichiometry.

112
Q

What is the molecular weight (Mr) used for ethanol (C₂H₅OH)?

A

46.0 g/mol

113
Q

What is the formula for calculating the amount of gas produced in a reaction?

A

Volume = nRT/P

This uses the ideal gas law where n is the number of moles, R is the gas constant, T is temperature in Kelvin, and P is pressure.

114
Q

What is the balanced chemical equation for the reaction of titanium chloride with sodium?

A

TiCl + 4 Na → 4 NaCl + Ti

115
Q

How do you calculate the amount in moles of a substance?

A

amount = mass / Mr

116
Q

Calculate the moles of TiCl from 100 g given a molar mass of 189.9 g/mol.

117
Q

Calculate the moles of sodium from 80 g given a molar mass of 23.0 g/mol.

118
Q

What is the limiting reactant when reacting TiCl with sodium?

119
Q

If 0.527 mol of TiCl is used, how many moles of Ti are produced?

120
Q

How do you calculate the mass of titanium formed from moles?

A

Mass = amount x Mr

121
Q

Calculate the mass of titanium formed from 0.527 mol given a molar mass of 47.9 g/mol.

122
Q

What is the formula for calculating percentage yield?

A

% yield = (actual yield / theoretical yield) × 100

123
Q

Calculate the percentage yield if 10.0 g of Fe is produced from a theoretical yield of 17.48 g.

124
Q

What is the formula for calculating % atom economy?

A

% atom economy = (mass of useful products / mass of all reactants) × 100

125
Q

What is the % atom economy for the reaction Fe2O3 + 3 CO → 2 Fe + 3 CO2?

126
Q

What is an ideal reaction in terms of atom economy?

A

A reaction with only one product where all atoms are used, resulting in 100% atom economy.

127
Q

What can improve the economics of a process with a side waste product?

A

Selling the by-product for other uses.

128
Q

What is the charge of lithium?

129
Q

What is the formula for lithium sulfate?

A

Li2SO4

Lithium has a +1 charge and sulfate has a -2 charge, requiring two lithium ions to balance the charge.

130
Q

What is the charge of calcium?

131
Q

What is the formula for calcium phosphate?

A

Ca3(PO4)2

Calcium has a +2 charge and phosphate has a -3 charge, requiring three calcium ions to balance two phosphate ions.

132
Q

What are spectator ions?

A

Ions that do not change state or oxidation number in a reaction.

133
Q

What is the formula for ammonium ion?

134
Q

What is the formula for sulfate ion?

135
Q

What is the charge of phosphate?

136
Q

What is the formula for nitrate ion?

137
Q

What is the formula for carbonate ion?

138
Q

What is the formula for hydroxide ion?

139
Q

How do you write an ionic equation?

A
  1. Separate (aq) solutions into ions 2. Cancel out spectator ions
140
Q

True or False: Ionic equations show all ions present in a reaction.

141
Q

What is the formula for copper(II) nitrate?

142
Q

What is the formula for calcium hydroxide?

143
Q

What is the charge of zinc?

144
Q

What is the charge of iron(II)?

145
Q

What is the charge of iron(III)?

146
Q

Fill in the blank: To combine ions into a neutral compound, the total positive charge must _______ the total negative charge.

A

cancel out

147
Q

List the key ions in Group 1.

A
  • Hydrogen
  • Silver
  • Gold
  • Ammonium (NH4)+
148
Q

List the key ions in Group 2.

A
  • Zinc
  • Copper (II)
  • Iron (II)
  • Tin
  • Lead
149
Q

List the key ions in Group 3.

A
  • Iron (III)
150
Q

List the key ions in Group 5.

151
Q

List the key ions in Group 6.

A
  • Carbonate (CO3)2-
  • Sulfate
152
Q

List the key ions in Group 7.

A
  • Nitrate (NO3)-
  • Hydroxide (OH)-

Chemistry (6 decks)

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