C3.1 - Introducing Chemical Reactions

Question 1

How are the formula of metals always written and why?

Answer 1

• As an empirical formula.
• Metals exist as giant metallic lattices - Don’t
  need to include the numbers because they are
  huge and would vary depending on the amount
  of metal.

Question 2

How do elements in Group 0 exist?

Answer 2

• Exist as individual atoms.
• Attracted to each other by weak intermolecular
  forces.
• Formula are the same as their chemical symbols.

Question 3

How do the elements of Group 7 exist?

Answer 3

• Diatomic molecules - Two atoms covalently
  bonded together.
• Attracted to each other by weak intermolecular
  forces.
• All elements have the subscript 2 in them.

Question 4

What 3 elements that aren’t in group 7 but also exist as diatomic molecules?

Answer 4

• Hydrogen
• Nitrogen
• Oxygen

Question 5

How does sulphur and phosphorus exist?

Answer 5

S8 and P4

Question 6

What does the molecular formula for a simple covalent compound show?

Answer 6

• The symbols for each element is contains.
• The number of atoms of each element in one of
  its molecules.

Question 7

What ions do metals in groups 1,2 and 3 produce?

Answer 7

The same number of positive charges as their non-IUPAC group number.

Question 8

What charges do transition elements make and what are 2 exceptions?

Answer 8

• Transition metals produce positive ions that
  usually have a 2+ charge.
• Silver - Ag+
• Iron(III) - Fe3+

Question 9

What charges do non metals in groups 5,6 and 7 produce?

Answer 9

Negative ions - 8 minus their (non-IUPAC) group number.

Question 10

What are compound ions?

Answer 10

Compound ions are ions that contain more than one element.

Question 11

What must be equal in any ionic compound?

Answer 11

The total number of positive and negative charges.

Question 12

What are the the chemical formula of the 5 compound ions?

Answer 12

Ammonium - NH4+
Hydroxide - OH-
Nitrate - NO3-
Carbonate - CO32-
Sulphate - SO42-

Question 13

What is the law of conservation of mass?

Answer 13

The principle that states that the total mass stays the same during a chemical reaction, because atoms are not created or destroyed during a chemical reaction.

Question 14

How can you investigate conservation of mass?

Answer 14

By carrying out a reaction in a closed system (a container in which no substances can enter or leave during the reaction).

Question 15

Why does the mass sometimes appear to go down during the reaction?

Answer 15

The reaction mixture may be a non-enclosed system and the reaction involves a substance in the gas state.

Question 16

What do state symbols show and what are the four state symbols?

Answer 16

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

• Solid (s)
• Liquid (l)
• Gas (g)
• Aqueous solution (aq)

Question 17

What is a half equation?

Answer 17

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

Question 18

How do you write a half equation?

Answer 18

• Write the element -> ion (or vice versa).
• Check to see if the full element is a diatomic and if
  it is balance it by adding a 2 behind the ion.
• Check the charges on each half of the equation
  and figure out how many electrons you need to
  take away or add.
• Write the amount of electrons you need with the
  coefficient being the number you need.

Question 19

What does an ionic equation show?

Answer 19

An ionic equation shows the ions present in a reaction mixture.

Question 20

What are spectator ions?

Answer 20

Ions that are in the reaction mixture but do not take part in the reaction.

Question 21

How is a net ionic equation different from a complete ionic equation?

Answer 21

A net ionic equation leaves out the spectator ions.

Question 22

Which state do you split into ions in for ionic equations?

Answer 22

Aqueous

Question 23

How do you write a compound ion in an ionic compound?

Answer 23

In brackets with the subscript being outside the bracket if there is one.

Question 24

What is Avogadro constant?

Answer 24

The number of entities in one mole of a substance, 6.02 x 1023 (3s.f.).

Question 25

What is the mole defined as?

Answer 25

The amount of any substance that contains the same number of entities (atoms, ions of molecules) as there are in 12.0g of carbon-12 atoms.

Question 26

What does one mole of water contain?

Answer 26

• 1 mole of water molecules.

- 3 moles of atoms.

Question 27

How can you measure a mole of a substance?

Answer 27

The mass of one mole of an element is its relative atomic mass which is also its molar mass (g/mol).

Question 28

What is the mass of a substance related to?

Answer 28

The mass of a substance is related to its molar mass and amount.

Question 29

What is the equation to calculate mass?

Answer 29

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

Question 30

What does the amount of product formed depend on?

Answer 30

The limiting reactant.

Question 31

What does stoichiometry describe?

Answer 31

The stoichiometry describes the relative amounts of each substance involved, and is to do with balancing numbers numbers.

Question 32

How to calculate the stoichiometry of a reaction?

Answer 32

• Calculate the amount (mol) of each measured
  substance.
• Simplify the ratio of each of the substances.
• Write the numbers in the equation.