chemistry paper 1- quantitative + chemical + energy changes

Question 1

How do you find the relative formula mass?

Answer 1

Find the relative atomic masses and add them together

Question 2

How to calculate the % mass of an element in a compound

Answer 2

Ar X no of atoms of the element
———————————————- X 100
Total of the compound

Question 3

what us the definition of a mole

Answer 3

an amount of a substance

Question 4

What is the Avogadro number?

Answer 4

6.02 X 10^23

Question 5

Formula for the no of moles

Answer 5

Mass in g of Ar
———————————-
Ar of the element

Question 6

What does it mean by conservation of mass?

Answer 6

During a chemical reaction no atoms are destroyed or created so theres the same number of atoms : no mass is lost or gained.

Question 7

What happens if mass does increase?

Answer 7

It increases as one of the reactants is a gas

Before the reaction the gas floats around as its not contained, mass cant be determined

When gas reacts to form the product it become contained in the reaction so the mass if the stuff inside the vessel increases

Question 8

what happens if mass decreased?

Answer 8

Because the product is a gas

Before the reaction all the reactants are contained

If it isn’t enclosed the gas can escape so it wont be contained : you can’t determine mass so total mass decreases of the stuff inside

Question 9

What happens when a reaction stops?

Answer 9

When one of the reactants gets used up so rest are in excess

Used up reactant = limiting reactant

Question 10

Why is the amount of product formed directly proportional to the amount of limiting reactant?

Answer 10

Because if you add more reactant there will be more reactant particles to take part in the reaction so more products particles

Question 11

What does concentration measure?

Answer 11

Measures how crowded things are

Question 12

Formula for concentration

Answer 12

Concentration = mass of solute
—-——————
volume of solvent

Question 13

What is concentration measured in ?

Answer 13

g/dm^3

Question 14

What does a ph of 0-6 mean?

Answer 14

Acids

Question 15

What does the ph of 8-14 mean?

Answer 15

Alkaline

Question 16

Neutralisation word equation?

Answer 16

Acid + base ——> salt + water

Question 17

HCl and HNO3 ionised

Answer 17

HCl——> H+ + Cl-

HNO3——> H+ + NO3-

Question 18

What are some strong acids features?

Answer 18

They can ionise completely in water

Particles dissociate to release H+ ions

Question 19

What are some weak acids features?

Answer 19

Don’t fully ionise in the solution

Only a small amount of particles dissociate to release H+ ions

Reversible reaction

Question 20

What are some features of the reactivity series?

Answer 20

In order of reactivity

Determined by how easily they lose electrons the higher the more essily they form positive ions

Question 21

Word equation for metal reacting with water

Answer 21

Metal+Water —> Metal Hydroxide + Oxygen

Question 22

What is oxidisation ?

Answer 22

Loss of electrons

Question 23

What is reduction?

Answer 23

Gain of electrons

Question 24

What are displacement reactions?

Answer 24

Redox Reactions

So a more reactive metal will displace a less reactive metal from its compound

Question 25

What happens during electrolysis?

Answer 25

An electric current oassed theough an electrolyte (a molten or dissolved ionic compound)

Ions move towards the electrodes where they react.

Positive ions will go the cathode where they gain electrons

Negative ions will go the cathode where they lose electrons

This creates a flow of charge through the electrolyte

Question 26

Why cant ionic solids be used in electrolysis?

Answer 26

As they are ions in fixed positions and cant move so molten ionic compounds need to be used

Question 27

How can metals be extracted from their ores ?

Answer 27

By using electrolysis:

•Aluminium is extracted from the ore bauxite by electrolysis

•Bauxite has aluminium oxide which is mixed with cryolite to lower the melting point

•The molten mixture has free ions= conducts electricity

•the positive ions to the negative electrode and pick 3 electrons which sink to the bottom of the tank

•the negative ions to the positive electrode and loose 2 electrons to form O2 molecules

Question 28

Test for chlorine?oxygen?hydrogen?

Answer 28

Chlorine: bleaches litmus paper turning white

Oxygen: relights a glowing splint

Hydrogen: squeaky pop with lighted splint

Question 29

What is an exothermic reaction?

Answer 29

Transfers energy to the surroundings e.g by heating

This is shown as there is a rise in temp

Like Combustion, Neutralisation

Question 30

What is an endothermic reaction?

Answer 30

Energy is taken in from the surrounding e.g fall in temp

Shown in thermal decomposition, ice pack

Question 31

RP for measuring the energy transfer

Answer 31

Take temp of the reagents + mix them in a polystyrene cup + measure temp of the solution at the end of the reaction

Reduce energy lost into the surroundings by insulating with cotton wool in the beaker

1- put HCl + Sodium hydroxide into separate beakers
2- place beakers in a water bath so they are at the same temp
3- add HCl then sodium hydroxide to the polystyrene cup with a lid
4-take temp of the mixture ever 30s + repeat with 0.5 and 1 mol/dm^3 of HCl

Question 32

Bond breaking and bond forming what process are they?

Answer 32

Breaking= endothermic

Forming= exothermic