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Chem GCSE > Chemistry Calcs > Flashcards

Chemistry Calcs Flashcards

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1
Q

Mr meaning

A

Relative formula mass

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2
Q

Ar meaning

A

Relative atomic mass

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3
Q

How do you calculate relative formula mass?

A

Periodic table mass number timsed by little number
Eg H= 1 O = 16
H20 = 2+16=18

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4
Q

How do you calculate RAM? (Ar)

A

Multiply percentage abundance by isotope mass number
Divided by 100

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5
Q

What is an isotope?

A

Different forms of the same element with the same amount of protons but different neutrons

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6
Q

Mass, moles and RAM equation

A

Mass = moles x RAM/RFM

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7
Q

What is avogadros number and what’s it used for?

A

6.0221x10 (power of 23)
- the amount of molecules in a mole

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8
Q

Definition of moles

A

A mole is the number of atoms in exactly 12g of carbon 12 (mol)

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9
Q

Mass of one mole of a substance is equal to

A

The relative atomic mass of formula mass

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10
Q

What is ionic bonding?

A

The electrostatic attraction between oppositely charged ions

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11
Q

1:2 ratio meaning

A

There is twice as much of the second compound/element to make up the other. =multiply by 2

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12
Q

What is a limiting reactant?

A

-first reactant to be fully used up
- brings reaction to an end

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13
Q

How can you ensure all the reactant has reacted in the reaction after it has stopped?

A

Add more excess reactant to see if the reaction continues

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14
Q

Percentage yield equation

A

Actual yield/g divided by theoretical yield /g multiplied by 100

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15
Q

Why is the theoretical yield bigger than the actual

A

If it’s a reversible reaction, loss of products (eg gasses)

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16
Q

Atom economy equation

A

Mass of useful products / mass of all products multiplied by 100
=?%

17
Q

Why is atom economy important?

A

Minimise energy and recourse cost, reduce pollution due to waste gasses, expensive recourses, raw materials are scarce so should be conserved

18
Q

If there are more by-products in a reaction is atom economy high or low

A

Lower if more waste products

19
Q

How can you increase atom economy?

A

Find a purpose/use for the products

20
Q

How do you calculate concentration from volume (v) moles (n)

A

n=cV
Moles = conc x volume

21
Q

What is conversion dm3 to cm3

A

X1000

22
Q

What is concentration measured in?

A

mol/dm3

23
Q

What is volume measured in?

A

dm3 or cm3

24
Q

Nitric acid formula

A

HNO3

25
Q

Sulphuric acid formuka

A

H2SO4

26
Q

Sodium sulphate formula

A

Na2SO4

27
Q

Phosphoric acid formula

A

H3PO4

28
Q

Sodium hydroxide

A

NaOH

29
Q

What is the purpose of a titration

A

To determine volume of solution needed to reach an endpoint eg colour change due to ph from phenolphthalein indicator

30
Q

Increased concentration means higher or lower ph

A

Lower as it becomes a stronger acid
=further from neutral 7

31
Q

Decreased concentration effect on ph

A

Increase ph means weaker acid = closer to neutral 7

32
Q

How do you mark an endpoint of a titration

A

Using indicator solution. When colour changes = endpoint.

33
Q

Avogadros law in terms of gasses

A

Equal volumes of gases at the same temp and pressure contain the same number of molecules should be volume 24dm3

33
Q

Avogadros law in terms of gasses

A

Equal volumes of gases at the same temp and pressure contain the same number of molecules should be volume 24dm3

34
Q

Gas volumes equation

A

Volume (dm3) = mol x 24

35
Q

Percentage composition equation

A

= RAM x no. Atoms of element needed / rfm of whole compound x 100

36
Q

Why is percentage yield not always 100%

A

Some product may be lost when separated from reactant mixture
Reversible reactions
Some reactants may react differently into other products

Chem GCSE (14 decks)

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