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Chemistry > Year 11 Term 2 > Flashcards

Year 11 Term 2 Flashcards

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1
Q

Conservation of mass

A

Mass is neither created nor destroyed during chemical processes, it’s conserved

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2
Q

Relative formula mass

A

The sum of the relative atomic masses of each atom in a compound

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3
Q

Reasons for uncertainty

A

Product or reactant is impure
The sample is wet
Gaseous products have escaped easily

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4
Q

What are measuring cylinders used for

A

To measure the volume of a liquid

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5
Q

How do you avoid a measurement error using a measurement cylinder

A

You have to measure to the bottom of the meniscus (the curve of the liquid being measured), also judge at eye level preventing parallax error

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6
Q

How to avoid a zero error when using a measuring cylinder

A

You have to set the syringe back at 0 before taking new reading otherwise you’ll get zero error where value appears larger than it would be

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7
Q

Top pan balance

A

Balance should always be tared (set at 0) before weighing to prevent zero error

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8
Q

Possible disruptions to measurement

A

People leaning on the table
Breeze blowing onto table
These will disrupt the balance

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9
Q

Possible contamination

A

Clear balance with soft paint brush before you measure anything so there’s no powder left on the balance

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10
Q

Uncertainty=

A

mean +/- the range of measurements

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11
Q

Why are moles useful

A

Allows chemists to calculate the required masses of reactants and it allows them to predict the mass of products for chemical reactions

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12
Q

What is a mole

A

The unit for the amount of substance. 1 mol of atoms, ions or molecules is around 6.03 x 10^23 which is the same number of carbon atoms in 12g of carbon

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13
Q

What is Agrovado’s number

A

6.03 x 10^23

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14
Q

What did Agrovado discover

A

If you have 6.03 x 10^23 atoms (1 mol) of an element, it will weigh its relative atomic mass (Ar) in grams

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15
Q

1 mol of any compound is equal to

A

Its relative formula mass

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16
Q

Mass =

A

Mr x mol

17
Q

What can Avrogado’s constant be used to calculate

A

The number of atoms/ molecules/ ions present in a given amount of a substance

18
Q

What are the coefficients in equations

A

The number in front of the formula, it’s proportional to the number of moles

19
Q

Why would knowing the molar ration be useful for the chemist who’s trying to conduct this reaction

A

Because mass= Mr x mol

so we can calc the mass of product that’ll be produced of the mass of reactant needed

20
Q

Using moles to balance equations

A

Divide mass by Mr to calculate moles on each
Divide each number of moles by the smallest to determine the ration
The molar ration is equivalent to the coefficients in the equation

21
Q

What’s the limiting reactant

A

If the number of moles of a reactant is less than the stoichiometric ratio tells us then it’s the limiting reactant
This will limit how far the reaction goes

22
Q

Why may reactions not always be perfect

A

Reaction may not go to completion as it’s reversible
Some of the product may be lost when separated from reaction mixture
Some of the reactants may react in ways different to the expected reaction

23
Q

What is the percentage yield

A

The amount of product obtained is the yield. When compared with the maximum theoretical amount as a % it’s called the percentage yield

24
Q

Percentage yield=

A

Actual yield/ theoretical yield x100

25
Q

What’s the theoretical maximum

A

The amount you calculate using mass= Mr x moles equation. It’s the amount you’d get if the reaction went fully to completion and no product was lost

26
Q

What’s atom economy

A

A measure of the amount of starting materials that end up as useful products

27
Q

Why is it important to use reactions with high atom economy

A

For sustainable and economic reasons as most chemical reactions produce 2 or more products but only 1 is useful so there’s waste from the process

28
Q

Atom economy=

A

Mr of desired product/ sum of Mr of all reactants x100

29
Q

What factors are there to consider when choosing an appropriate method besides atom economy

A

% yield
Reaction rate
Reversibility
Energy cost

30
Q

How do you convert from cm cubed to dm cubed

A

Divide by 1000

31
Q

1 dm^3 is equal to

A

1 litre

32
Q

Concentration =

A

Quantity of solute/volume

33
Q

Factors affecting concentration

A

If you double volume, you half the concentration

If you halve the volume, you double the concentration

34
Q

How do you convert from mol/dm^3 to g/dm^3

A

Multiply by Mr

35
Q

How do you convert from g/dm^3 to mol/dm^3

A

Divide by Mr

36
Q

Number of moles =

A

Concentration (mol/dm^3) x Volume (dm^3)

n=cv

Chemistry (13 decks)

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