Chapter 4: Chemical Reactions

Question 1

What is the difference between an exothermic and endothermic reaction?

Answer 1

exothermic gives out energy while endothermic takes energy in (needs energy to take place)

Question 2

What is the law of conservation of mass?

Answer 2

total mass before (reactants) = total mass after (products)

Question 3

What is a synthesis reaction?

Answer 3

-a compound made from simpler materials
-A+B= C

Question 4

What is a decomposition reaction?

Answer 4

-a compound that is broken down into simpler compounds or all the way broken down into it’s elements
-AB = A + B

Question 5

What is combustion?

Answer 5

-the burning of an element or a compound in oxygen or air.
-CH^4(g) + O^2 = CO^2(g) + 2H^2O(l)

Question 6

define oxidation:

Answer 6

the addition of oxygen to an element or a compound (loss of electrons)

Question 7

define reduction:

Answer 7

the removal of oxygen from a compound (gain of electrons)

Question 8

What happens to the charge of an ion when it gains electrons?

Answer 8

the charge decreases (eg if an ion with with charge 4+ gains 2 electrons then the charge is now 2+)

Question 9

What is precipitation?

Answer 9

the sudden formation of a solid, either when two solutions are mixed or when a gas is bubbled in a solution.

Question 10

How to find the ionic equation?

Answer 10

1. write out the balanced chemical equation
2. rewrite the whole equation in terms of the ions present
3. take out the spectator ions
4. write out balanced ionic equation

Question 11

How do you work out the empirical formula?

Answer 11

1. write out all the components of the molecule and work out their number of moles
2. put the number of moles of each element into a ratio
3. simplify to whole numbers
4. write out equation