Module 2 - Foundations in Chemistry - Exam Questions Flashcards
Define relative isotopic mass (2)
Mass of the isotope compared to 1/12th of the mass of a carbon 12
Define isotopes (1)
Atoms with the same number of protons but a different number of neutrons
Explain why isotopes have the same chemical properties (1)
Same number of electrons in the outer shell
Define relative atomic mass (3)
The weighted mean mass of an atom relative to 1/12th the mass of one atom of carbon 12
How could the fraction of the isotopes of carbon be found experimentally? (1)
Mass spectrometry
Explain what is meant by a salt (1)
When the H+ in an acid is replaced by a metal ion
What term is given to the .n H2O part of a formula? (1)
Waters of crystallisation
What calcium compound is formed when calcium oxide reacts with water? (1)
Calcium hydroxide
What calcium compound is formed when calcium oxide reacts with nitric acid? (1)
caO(s)+2HNO3(aq)→Ca(NO3)2(aq)+H2O(l)
forms calcium nitrate
How do old samples of magnesium oxide become contaminated with magnesium carbonate? (1)
MgO has reacted with CO2
A student adds an excess of HCl to magnesium oxide and magnesium carbonate, state two observations that would be made (2)
Solid dissolves
Effervescence
Define an acid (1)
A proton donor
How can CaCO3 be used to combat excess stomach acid? Use an equation (2)
CaCO3 neutralises HCl
CaCO3 + 2HCl -> CaCl2 + H2O + CO2
State an important use of ammonium sulphate (1)
Fertiliser
State a large-scale use of ammonia (1)
Manufacture of explosives
Use oxidation numbers to explain why the reaction involves both oxidation and reduction (algebraically) (3)
X: oxidation number goes up
Y: oxidation number goes down
X is oxidised and Y is reduced
Explain, in terms of electrons, what is meant by oxidation (1)
Loss of electrons
What is meant by the term mole? (1)
Amount of substance that has the same number of particles as there are atoms in 12g of carbon 12
What is NaClO? (1)
NaClO is Bleach
Define empirical formula (1)
Simples whole number ratio of atoms
After Ca has fully reacted with HCl, upon adding more Ca, a reaction still takes place, why? (3)
Ca has reacted with water
Ca + 2H2O -> Ca(OH)2 + H2
Explain what is meant by molecular formula (1)
Number and type of atoms making up a molecule
What is meant by ionic bonding? (1)
Electrostatic attraction between oppositely charged ions
Predict the bond angle in an F2O molecule and explain (3)
104.5
There are 2 bonded pairs and 2 lone pairs
Lone pairs repel more than bonded pairs
Describe and explain two anomalous properties of water from hydrogen bonding (4)
Liquid H2O is more dense than solid
Ice has open lattice
H2O has a relatively high boiling point
Hydrogen bonds need to be broken
Magnesium melting point: 650°C
Chlorine melting point: -101°C
Describe the structure and bonding of these elements and explain the difference in melting points (6)
Mg has a giant structure
Mg has metallic bonding
Electrostatic attraction between positive ions and electrons
Cl has a simple covalent lattice
Cl has induced dipole-dipole
Less energy is needed to overcome induced dipole-dipole than metallic bonds
Describe the bonding and structure in graphite
Explain why graphite is a good conductor, a soft material and a very high melting point (5)
Giant covalent lattice Arranged in layers Good conductor - mobile electrons High melting point - covalent bonds have to be broken Soft - weak forces between the layers
What is meant by a covalent bond? (1)
A shared pair of electrons
Name the shape of the ammonia molecule and why ammonia has this shape and a bond angle of 107° (3)
ammonia NH3
Pyramidal
There are 3 bonded pairs and 1 lone pair
Lone pairs repel more than bonded pairs
Why does ammonium chloride not conduct electricity when solid but does when dissolved in water? (2)
Ions cannot move in a solid
Ions can move in solution
What is meant by metallic bonding? (2)
Electrostatic attraction between the delocalised electrons and the positive ions
Why does H2S have a much lower boiling point than H2O? (2)
No hydrogen bonding
Weaker intermolecular forces
What is meant by hydrogen bonding? (1)
Interaction between lone pair of F, N or O and a H in a neighbouring molecule
Explain electronegativity (2)
Attraction of an atom for electrons in a covalent bond
Why do O-H and N-H bonds have dipoles? (1)
Oxygen and nitrogen are more electronegative than hydrogen
Why does a water molecule have a different shape to a carbon dioxide molecule? (2)
Electron pairs repel
Oxygen in water has 2 bonds and 2 lone pairs
Carbon in CO2 has 2 double bonds
Why is water a polar molecule, but CO2 is not?
CO2 is symmetrical
In CO2, dipoles cancel
