C3: Chemical reactions, formulae and equations

Question 1

What happens in all chemical reactions?

Answer 1

In all chemical reactions, the atoms in the reactants are rearranged to make new substances called the products. For example, when hydrogen reacts with oxygen, the atoms in the hydrogen and oxygen molecules rearrange to form molecules of the new substance, water.

Question 2

what is the law of conservation of mass?

Answer 2

No atoms are created or destroyed in a chemical reaction. This means that the total mass of all the reactants will equal the total mass of all the products. For example, when 4 g of hydrogen reacts with 32 g of oxygen, the atoms rearrange to make 36 g of water.

Question 3

state the formula for ammonia, carbon monoxide, methane, nitrogen dioxide, nitrogen monoxide, sulfur dioxide and sulfur trioxide

Answer 3

ammonia- NH3
carbon monoxide- CO
methane- CH4
nitrogen dioxide- NO2
nitrogen monoxide- NO
sulfur dioxide- SO2
sulfur trioxide-SO3

Question 4

State the charges of group 13 and 16 ions

Answer 4

Group 13 ions: Al3+

Group 16 ions: O2− oxide, S2− sulfide

Question 5

State the charges of other + ions

Answer 5

other positive ions: NH4+ ammonium, Cu2+ copper(II), Ag+ , Zn2+

Question 6

state the formula of common acids

Answer 6

nitric acid- HNO3
sulfuric acid- H2SO4
ethanoic acid- CH3COOH

Question 7

These formulae of common covalent elements should also be learned.

Answer 7

bromine- Br2
buckminsterfullerene- C60
nitrogen- N2
oxygen- O2

Question 8

what are ionic equations?

Answer 8

An ionic equation can be written that leaves out any ions that do not take part in the reaction- spectator ions. State symbols in ionic equations are included.

Question 9

Write the ionic equation for acid reacting w alkali

Answer 9

acid + alkali

H+(aq) + OH−(aq) → H2O(l)

Question 10

Write the ionic equation for acid + carbonate?

Answer 10

acid + carbonate

2H+(aq) + CO32−(aq) → H2O(l) + CO2(g)

Question 11

Write the ionic equation for acid + ammonia?

Answer 11

acid + ammonia

H+(aq) + NH3(aq) → NH4+(aq)

Question 12

what are redox reactions?

Answer 12

In redox reactions, including displacement reactions and electrolysis, two half-equations can be written to show the reduction and oxidation processes separately. These half-equations show the gain or loss of electrons.

Question 13

give redox reaction examples

Answer 13

For example, in the electrolysis of molten aluminium oxide: Al3+ ions gain electrons to become Al, and O2− ions lose electrons to become O2.

Al3+ to Al. Each Al3+ ion gains 3 electrons:
Al3+ + 3e− → Al

O2− to O2. Two O2− ions are needed to make O2 and each O2− ion loses 2 electrons:
2O2− → O2 + 4e−

Question 14

Describe displacement reactions and their half equations

Answer 14

For example, when copper displaces silver from a solution of silver nitrate: the copper atoms lose electrons to form copper ions and the silver ions in silver nitrate gain electrons to form silver. The nitrate ions do not react.

Ag+ to Ag Each Ag+ ion gains 1 electron: Ag+ + e− → Ag
Cu to Cu2+ Each Cu atom loses 2 electrons: Cu → Cu2+ + 2e−

Question 15

what is a reversible reaction?

Answer 15

Many chemical reactions are reversible. This means that the products of the reaction can turn back into the reactants

Question 16

What happens when equilibriums lies to the left towards the right?

Answer 16

When eqm lie to the right: lots of product not much reactant

When eqm lies to the left: lots of reactant, not much product.

Question 17

what happens if u change a system in eqm?

Answer 17

If the conditions of a system in a state of dynamic equilibrium are changed, the position of the equilibrium moves to oppose that change.

Question 18

What happens if you increase reactant concentration to a reaction in equilibrium?

Answer 18

The rate of the forward reaction increases and more product will form. As product conc increases, the rate of backward reaction increases to reach new eqm position to the right. Therefore hay mas product. Decreasing reactant concentration shifts equilibrium to the left.

Question 19

What happens if you increased product concentration in an equilibria reaction?

Answer 19

The rate of the backwards reaction increases and more reactant forms. As reactant conc increases, the rate of the forward reaction increases to reach a new eqm position to the left. Decreasing product concentration shifts to the right

Question 20

How do you increase or decrease the pressure of reaction?

Answer 20

Reducing the volume, using more moles of reactants in the same volume.
Pressure is decreased by increasing the volume or using less moles of reactants in the same volume.

Question 21

Describe the effect of pressure on a reaction in equilibria

Answer 21

Increasing pressure shifts to the side with the fewest gas moles. Decreasing pressure shifts to the side with more moles of gas. If the number of moles of the same on both sides, there is no change. Pressure only applies to reactions with gases at a given temperature.

Question 22

Describe the effect of temperature on a reaction in equilibria

Answer 22

Increasing temperature increases the rates of both forwards and backwards reactions, but there will be greater increase and the eqm will shift to the endo side. Decreasing temperature shifts to the exo side