R2.1: How Much? The Amount Of Chemcial Change

Question 1

What happens in a chemical reaction?

Answer 1

New substances produced
No overall change in mass
Fixed relationship between number of reactant particles and number of product particles

Energy change occurs -> bonds in reactants broken and new bonds formed

Question 2

How do you balance equations?

Answer 2

Same number of atoms of each element on both sides of the equation

1. Write formula of the reactants and products
2. Count the number of atoms in each reactant (take into account coefficients)
3. Balance atoms one at a time (using coefficient) until all atoms are balanced
4. Use appropriate state symbols!!!

Question 3

What is the ionic equation of reacting silver nitrate solution and sodium chloride solution?

Answer 3

Équation that shows that shows how negative and positive ions combine to form a compound

Eg:
Silver nitrate solution + sodium chloride solution -> white precipitate (silver chloride)

AgNO3 (aq) + NaCl (aq) -> NANO3 (aq) + AgCl (s)

Na+ (aq) and NO3- (aq) -> secptator ions

Ionic equation for silver chloride:
Ag+ (aq) + Cl- (aq) -> AgCl (s)

Question 4

What is the half equation of reacting zinc metal and copper (II) sulphate?
What is the overall reaction?

Answer 4

Half equations: show change in oxidation state

Zn (s) -> Zn2+ (aq) + 2e-
Cu2+ (aq) + 2e- -> Cu (s)

Ionic equation: Zn (s) + CU2+ (aq) -> Zn2+ (aq) + Cu (s)
Overall equation: Zn (s) + CuSO4 (aq) -> ZnSO4 (aq) + Cu (s)

Question 5

What is the equation for moles?
What is the information needed to find the mass of product?

Answer 5

Moles = mass/molar mass

Mass of reactants
Molar mass of reactants
Balanced equation

Question 6

What us avogardo’s law?

Answer 6

That equal volumes of gas must contain the same number of molecules
- enables mole ratio of reacting gases to be determined form volume of gas

At STP (273 K, 100kPa) one mole of any gas -> 22.7 dm3/mol

Question 7

What is the equation for the volume of a given amount of gas?

Answer 7

Volume of gas (dm3) = amount of gas (mol) x 22.7 dm3/mol

Question 8

Équation for the concentration of a solution

Answer 8

1 molar solution = 1 mole of solute in solvent with total come dm3

Concentration = mass or moles of solute / total volume