C3.1 - Chemical Reactions

Question 1

How are the formulae of Metals written and why?

Answer 1

The formulae for metal elements are always written as the empirical formula because metals exist as giant metallic lattices, and so the numbers of atoms are very large and vary.

Question 2

Which elements are diatomic?

Answer 2

• All elements in group 7 (halogens) exist as diatomic molecules
• (also) hydrogen, nitrogen and oxygen.

Question 3

How does phosphorus exist?

Answer 3

P4

Question 4

What does the molecular formula of a compound show?

Answer 4

• the symbols of each element
• the number of atoms of each element

Question 5

what are the 5 compound Ions?

Answer 5

Ammonium - NH4 +
Hydroxide - OH -
Nitrate - NO3 -
Carbonate - CO3 2-
Sulfate - SO4 2-

Question 6

What is the law of conservation of mass?

Answer 6

Atoms cannot be created or destroyed by chemical reactions. The same atoms are present at the start and end of a reaction, so the total mass remains the same (in a closed system).

Question 7

What does a balanced equation show?

Answer 7

• How the atoms are rearranged in a reaction
• The relative amounts of each substance involved

Question 8

What are state symbols?

Answer 8

State symbols show the physical state of each substance in a chemical reaction.

Question 9

What is a half equation?

Answer 9

A half equation is a model for the change that happens to one reactant in a chemical reaction.

Question 10

What is a complete ionic equations?

Answer 10

A complete ionic equation shows the ions present in a reaction mixture.

Question 11

What are spectator ions?

Answer 11

Spectator Ions appear in the form on both sides, and do not take part in the reaction.

Question 12

What is a net ionic equation?

Answer 12

A net ionic equation shows the ions present in a reacting mixture, leaving out the spectator ions.

Question 13

What is a precipitate?

Answer 13

An insoluble product.

Question 14

What is a mole?

Answer 14

The mole is a unit for measuring the amount of something. One Mole of any substance contains the same number of entities as there are atoms in 12.0g of carbon-12 atoms.

Question 15

What is the Avogadro Constant?

Answer 15

The Avogadro constant is the number of entities in 1 mol of a substance.
6.02 x 10^23

Question 16

What is molar mass?

Answer 16

The molar mass is the mass of 1 mol of a substance (the relative atomic/formula mass in grams). It is measured in g/mol.

Question 17

How can you relate mass, molar mass, and amount (mol).

Answer 17

mass (g) = molar mass (g/mol) x amount (mol)

Question 18

What is a limiting reactant and excess reactant?

Answer 18

One reactant is usually in excess, and more of it is present that needed, so some is left at the end. The other reactant is limiting, and the amount of product formed is determined by the limiting reactant.