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GCSE Chemistry Paper 1 v2 > Quantitative Chemistry > Flashcards

Quantitative Chemistry Flashcards

1
Q

How do you work out the number of moles in a liquid?

A

N=volume*concentration

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2
Q

What is relative formula mass?

A

All the atomic masses of all the atoms in the molecular formulas added up.

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3
Q

What number is the atomic mass?

A

The top number always the biggest

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4
Q

How do you calculate the percentage mass of an element in a compound?

A

=(relative atomic massnumber of atoms of that element/Mr of the compound)100

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5
Q

What is a mole?

A

It is an measurement. 1 mole = 6.02*10^23. The mass of that number of atoms is always the same number of grams as the relative atomic mass of that substance.

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6
Q

How much would one mole of Carbon weigh?

A

12g

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7
Q

How much would one mole of Nitrogen gas weigh?

A

28g

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8
Q

How do you work out moles?

A

Number of moles=mass/Mr

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9
Q

What is the law of conservation of mass?

A

This is the rule that is a reaction atoms are not created or destroyed. This means there is the same number of atoms on each side of the equation.

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10
Q

When would you observe a change of mass in a reaction?

A

When a gas is being p[produced and you have an unsealed reaction vessel during a reaction.

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11
Q

How would the reaction increase in mass?

A

If the gas within the air reacts to form one of the products the mass will increase. For example when a metal reacts with oxygen in an unsealed container. So the product will form metal oxide and the oxygen that was not accounted for in the air has been added.

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12
Q

How would the reaction decrease in mass?

A

Before the reaction all of the reactants were. If the reaction vessel is not enclosed then gas can escape as its formed. Its no longer contained in the vessels so you can not account for its mass. For example when a metal carbonate thermally decomposes to form a metal oxide and carbon dioxide which will dissipate to the outside.

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13
Q

What is adding a substance in excess and why do we do this?

A

This is where we add extra of the substance so it is not a limiting factor and all the other substance is used up in the reaction.

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14
Q

What is the limiting factor?

A

The reactant that is used up in an equation. The amount of product formed is directly proportional to the limiting factor.

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15
Q

How do you work out the mass of the product with the limiting factor?

A

Write out the balanced equation
Work out relative formula mass of the reactant and product
Find out the moles of the substances you know.
You can use the law of conservation of mass to work out the moles of the other reactant. In this case, that’s how many moles of product will be made of this many moles of reactant.
Use the number of moles to calculate mass.

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16
Q

What is yield?

A

This is the mass of a product. On paper masses we calculate are theoretical yields. In practice you never get 100% of the yield.

17
Q

At room temperature and pressure how much volume does one mole of gas take up?

A

24dm^3

18
Q

How do you work out the volume of gas?

A

volume of gas=(mass of gas/Mr of gas)*24

19
Q

What is concentration?

A

The amount of substance in a certain area. The more solute there is in a given volume the more concentrated.

20
Q

How do you calculate concentration?

A

concentration=mass of solute/volume of solvent

concentration=number of moles of solute/volume of solvent

21
Q

What is the unit of concentration?

A

g/dm^3

mol/dm^3

22
Q

How do you work out concentration?

A

Concentration=no. moles/volume

mol/dm^3

23
Q

How do you convert cm^3 into dm^3?

A

*1000

24
Q

How do you convert mol/dm^3 into g/dm^3?

A

mass=moles*Mr

25
Q

What is atom economy?

A

It is a way to tell you how much of the mass of the reactants is wasted when manufacturing a chemical and how much ends up as useful products.

26
Q

How do you work out atom economy?

A

(RFM of desired product/RFM of all reactants)*100

27
Q

How do you work out percentage yield?

A

=(mass of product actually made/maximum theoretical mass of product)*100

28
Q

Why are yields always below 100%?

A

Products are always lost during a real life reaction. Some reactants could react with air or impurities in the reaction.

GCSE Chemistry Paper 1 v2 (5 decks)

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