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Quantitative chemistry (seneca) Flashcards

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1
Q

total mass of reactants=

A

total mass of products

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2
Q

relative formula (molecular) mass(Mr)=

A

Σrelative atomic mass(Ar)

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3
Q

Σrelative atomic mass(Ar)=

A

relative formula (molecular) mass(Mr)

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4
Q

what does ‘Σ’ mean?

A

used to denote a sum of multiple terms

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5
Q

what does relative formula mass mean?

A

the sum of the relative atomic of each atom in the formula

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6
Q

what does relative atom mass mean?

A

average mass of the atom

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7
Q

what is the formula for ethanol

A

C2H6O

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8
Q

why would a chemical measurement involves some uncertainty.

A

a digital thermometer is able to measure to a precision of 0.1oC.
If this thermometer displayed a reading of 35.4oC, the actual temperature could be anywhere between 35.35oC and 35.45oC

-

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9
Q

The molecular formula shows …

A

the actual amount of atoms which make up a molecule.

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10
Q

whats the molecular formula for glucose

A

C6H12O6

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11
Q

The empirical formula shows…

A

the simplest ratio of atoms which make up a molecule.

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12
Q

what the empirical formula for glucose?

A

CH2O

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13
Q

The empirical formula is also knowns as the

A

simplest formula

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14
Q

The molecular formula is also knowns as the

A

actual formula

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15
Q

Because atoms and molecules are so small, it is inconvenient to talk about individual atoms.
Instead, chemical amounts can be measured in …

A

moles

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16
Q

1 mole of a substance is _______ of that substance

A

6.02x10 to the power of 23 atoms

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17
Q

6.02x1023 is called the …

A

Avogadro constant

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18
Q

what the molecular formula for sulfuric acid

A

H 2 SO 4

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19
Q

what the molecular formula for sodium sulfate

A

Na2SO4

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20
Q

balanced symbol equations can be interpreted in units of…

A

moles

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21
Q

Mr stands for…

A

Relative formula mass

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22
Q

Ar stands for…

A

Relative atomic mass

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23
Q

moles=

​

A

mass/relative formula mass

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24
Q

mass/relative formula mass=

A

moles

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25
Q

The reactant that is completely used up is called the ——– because …

A

limiting reactant
the reaction stops when it is used up.

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26
Q

A reactant that is ———–is called the limiting reactant.

A

completely used up in a reaction

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27
Q

when a substance is dissolved in solution, we use the solution ‘s concentration to calculate the …

A

number of moles

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28
Q

we can measure concentration using different units:

A

grams per decimetre cubed or
moles per decimetre cubed

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29
Q

grams per decimetre cubed=

A

the mass of a dissolved solid in a solution/volume of solution

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30
Q

moles per decimetre cubed=

A

the moles of a dissolved solid in a solution/ volume of the solution

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31
Q

concentration (—–)=

A

mol/dm3
moles (mol) ÷ volume (dm3)

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32
Q

The units of concentration can be …

A

g/dm3
mol/dm3
M

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33
Q

Concentration (—–) =

A

g/dm3
mass (g) ÷ volume (dm3)

34
Q

When neutralising an acid, it is important that there’s no (1) left after the reaction. To make sure this happens, we use an (2)
(‘more than necessary’) amount of the other reactant.

A
  1. acid
  2. excess
35
Q

number of moles=

A

mass(g)/ relative atomic mass Ar

36
Q

The percentage yield for any reaction is always

A

less than 100%

37
Q

It might be —- to fully separate the product from the reaction mixture.

A

difficult

38
Q

An incomplete reaction can happen because

A
  • The reaction is very slow and hasn’t been given enough time to happen.
  • The reaction is reversible and some of the products have been converted back into reactants.
39
Q

Unexpected reactions (side reactions) can happen. This may mean that…

A

the intended product is not created.

40
Q

Some of the chemicals will remain stuck to the apparatus and will be …

A

wasted.

41
Q

percentage yield =

A

(real yield/theoretical yield)x100

42
Q

what is a percentage yield?

A

A comparison of the real and theoretical yields of a reaction.

43
Q

The real yield is …

A

the mass of a desired product obtained from a reaction.

44
Q

The theoretical yield is …

A

the maximum mass of a product that could possibly be created from a reaction.

45
Q

The theoretical yield can be calculated from …

A

a balanced equation if we know the mass of the reactants.

46
Q

what are the 4 factors that reduce percentage yield

A

-Separation difficulties
-Chemicals stick to apparatus
-Side reactions
-Incomplete reactions

47
Q

theoretical yield=

A

(real yield÷ % yield) × 100

48
Q

real yield=

A

(% yield × theoretical yield)÷100

49
Q

atom economy(%)=

A

total relative molecular mass of all reactants /relative molecular mass of desired products × 100

50
Q

Which term is used to describe the amount of the reactants that end up as useful products?

A

atom economy

51
Q

second formula
Atom economy =

A

(Mr of desired products ÷ Mr of all reactants) x 100%

52
Q

what is cost-effectiveness?

A

Using the smallest possible amount of reactants saves money.

53
Q

A higher atom economy means that —- waste is produced.

A

less

54
Q

When selecting a reaction pathway, we don’t just consider atom economy. We also look at:

A

-How much the reactants cost.
-What the percentage yield will be.
-How quickly the reaction will happen.
-How useful the by-products of the reaction are.
-The position of equilibrium

55
Q

what is chemical equilibrium?

A

A state in a reaction where the rate of the forward reaction is equal to the rate of the reverse reaction

56
Q

Finding ways to make the —- products of chemical reactions useful can increase the atom economy.

A

waste

57
Q

what term is used to describe the amount of the reactants that end up as useful products?

A

atom economy

58
Q

atom economy can also be called…

A

atom utilisation

59
Q

Mᵣ of desired products=

A

(Atom economy × Mᵣ of all reactants)÷100

60
Q

We can calculate the concentration of a solution if we know:

A

-The volumes of 2 solutions that react completely.
-The concentration of 1 of these solutions.

61
Q

We can calculate the amount of a solute (dissolved substance) in a solution if we know:

A

-The concentration of the solution.
-The volume of the solution.

62
Q

what is a solution?

A

The mixture formed when a solute has dissolved in a solvent.

63
Q

what is a solute?

A

The substance that dissolves in a liquid to form a solution.

64
Q

what is a solvent?

A

The liquid in which a solute dissolves.

65
Q

Concentration of a solution (—–) =

A

mol/dm3
amount of solute (mol) ÷ volume (dm3)

66
Q

1 mole of a gas will take up

A

24 dm3 at room temperature (20°C) and pressure (1 atm)

67
Q

When given the volume of 1 gas involved in a reaction between gases,

A

the balanced equation for the reaction can be used to calculate the volume of any other component.

68
Q

volume (—-) =

A

dm³
mass of substance (g) ÷ Concentration of a solution (g/dm³)

69
Q

How could you reduce the uncertainty in the pipette reading?

A

repeat the experiment and calculate an average

70
Q

What information is needed in order to calculate the mass of a substance if we know the number of moles of substance?

A

Mr of the substance

71
Q

How much volume does 1 mole of gas occupy at 20°C temperature and 1 atm pressure?

A

24 dm3

72
Q

Define the term ‘limiting reactant’ and calculate which reactant is limiting in the equation.

A

The limiting reactant is the reactant that is completely used up. As a result of this, it limits the amount of product.

73
Q

1 cm3 =

A

0.001dm3

74
Q

the limiting reactant is the reactant with —– moles

A

less

75
Q

why would a reaction that releases a gas have a percentage less than 100%

A

Some of the gas might have escaped between starting the reaction and fitting the bung.

Some of the gas might have escaped if the bung was not fitted tightly or if there was a leak in the syringe.

Some of the limiting reactant might not have reacted meaning that not all the product was actually produced.

76
Q

what does concordant results mean?

A

If readings have been taken several times and the readings are identical, or close to each other

77
Q

This question concerns gases.

2 mole of methane (CH3(g)), 2 mole of diatomic chlorine (Cl2(g)) and 2 mol the noble gas argon (Ar(g)) were each pumped into 3 identical balloons.
Which balloon will be the biggest?

A

all the balloons will be the same size
The volume of one mole of gas at a given temperature and pressure will be the same as one mole of any other gas under the same conditions.

78
Q

The volume of one mole of gas at a given temperature and pressure will be

A

the same as one mole of any other gas under the same conditions.

79
Q

what is sodium nitrate’s relative formula

A

NaNO3

80
Q

what is calcium nitrate’s relative formula

A

Ca(NO3)2

81
Q

in the equation 2Fe2O3 + 3C → 4Fe + 3CO2, what is the ratio of Fe2O3
and CO2

A

2:3

science chemistry (18 decks)

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