The Periodic Table
What does Group number tell us?
The number of valence electrons the element has.
An acid reacts with a base in a neutralisation reaction. Identify its products.
salt + water
Describe a precipitation reaction.
A precipitation reaction occurs when two soluble reactants combine to form an insoluble product known as the precipitate.
Classify the following reaction:
HNO3 + KOH --> KNO3 + H2O
Neutralisation
A nitrogen atom can form a nitride ion with the formula N3-. What is the number of electrons in the outer shell of a nitrogen atom?
5 electrons
Why are atoms neutral?
The positively charged protons cancel out the negatively charged electrons.
Why do we balance equations?
We balance equations due to the Law of Conservation of Mass. During a chemical reaction, atoms cannot be created or destroyed.
Predict the precipitate formed when the following solutions are mixed:
silver nitrate and sodium chloride
silver chloride
Use the reactivity series to describe what would happen if a piece of lead is dipped into a solution of silver nitrate.
Lead will displace silver as it is more reactive than silver.
What is an isotope?
Isotopes are a form of the same element, which contain the same number of protons (same atomic number) but a different number of neutrons (different mass number).
Magnesium atoms have 12 electrons arranged in the electron configuration 2, 8, 2.
Determine the period and group for Magnesium.
Group 2, Period 3
Provide a balanced equation for the following:
Aluminium reacts with oxygen in the air to form aluminium oxide.
4Al + 3O2 2Al2O3
Compare combination and decomposition reactions.
Combination reactions combine several reactants into one product. Decomposition reactions form several products from one reactant.
Briefly describe redox reactions.
Redox reactions occur when two processes, reduction and oxidation, take place at the same time.
In oxidation, a substance provides the electrons, whereas in a reduction a different substance gains electrons.
Describe the difference between excited state and ground state.
Ground state is when electrons are in their lowest energy level, whereas excited state is where electrons jump to higher energy levels.
Nitrogen, N, is in period 2, group 15. Suggest an element would have properties most similar to nitrogen?
Phosphorus (or any group 15 element).
Add the correct coefficients to balance the following equation.
ZnS + O2 --> ZnO + SO4
2, 3, 2, 2
What are the word and formula equations for the following reaction?
A solution of aluminium chloride reacts with a solution of magnesium sulfate to form a precipitate.
aluminium chloride solution + magnesium sulfate solution → magnesium chloride solution + aluminium sulfate solution
AlCl3 (aq) + MgSO4 (aq) → MgCl2 (aq) + Al2(SO4)3 (aq)
What happens during combustion reactions?
Substances burn rapidly in oxygen and produce large amounts of heat and light.
What is the total number of atoms present in the following: 2Na3PO4 ?
16 atoms
Explain what is meant by atomic number and mass number.
The atomic number is equal to the number of protons in the nucleus of an atom. The atomic number identifies the element.
The atomic mass is the number of protons AND neutrons in the nucleus.
Marble chips are a form of calcium carbonate. When they react with hydrochloric acid, they produce calcium chloride, carbon dioxide and water. Write a balanced chemical equation for this reaction (with states).
CaCO3 (s) + 2HCl (aq) --> CaCl2 (aq) + H2O (l) + CO2 (g)
Balance the following half-equations by working out how many electrons are gained or lost. Classify each equation as either reduction or oxidation.
a) Na --> Na+
b) Al3+ --> Al
a) oxidation
Na --> Na+ + 1e
b) reduction
b) Al3+ + 3e --> Al
Powdered zinc metal was added to a silver (I) nitrate solution. Silver metal formed and sank to the bottom of a zinc nitrate solution.
a) Write a word equation
b) Write a balanced formula equation
c) Classify this type of reaction
a) Zinc + silver nitrate --> silver + zinc nitrate
b) Zn (s) + 2AgNO3 (aq) → 2Ag (s) + Zn(NO3)2 (aq)
c) Metal displacement
Compare endothermic and exothermic reactions.
In exothermic reactions the chemical energy stored in the reactants is released as heat or light when the products are formed. In endothermic reactions the reactants absorb heat when the product is formed. This makes endothermic reactions feel cold.