Chemistry Unit 1
Write a balanced equation to show how ammonium sulfate could be formed by the reaction between aqueous ammonia and sulfuric acid
2NH3 + H2SO4 -> (NH4)2SO4
Complete the electron configuration for a titanium atom
2s2 2p6 3s2 3p6 4s2 3d2 4s2
Write an equation for the reaction of sodium with oxygen to form sodium oxide (Na2O)
4Na + O2 -> 2Na2O
State the approximate pH value of the Ba(OH)2 solution
7<x>15
Calculate in mol the amount of H20 removed
1.57/18 = 0.0872 mol
Using avogadro constant, calculate the number of carbon atoms in 0.321g of pencil lead
1.61 x 10(^22) (0.0268 x 6.02 x 10(^23)
Predict the bond angles in an F2O molecule
104.5 as there are 2 bonded pairs and 2 lone pairs. Lone pairs repel more than bonded pairs
What is the relative formula mass of (NH4)2SO4?
132.1
Calculat the concentration in moldm-3 of Ba(OH)2 solution formed
8.0 x 10-3
Calculate the volume of hydrogen in cm3 produced at RTP
19.2
Complete the electron configuration of the Cl- ion
1s(^2)2s(^2)2p(^6)3s(^2)3p(^6)
Calculate the relative atomic mass of the sample of Mg. 24Mg: 78.6% 25Mg: 10.11% 26Mg: 11.29%
24.33
Why is ammonia acting as a base in this neutralisation
It accepts a proton
Calculate the value of x in MgSO4•xH20
X = 7
The mass of the pencil lead was 0.321g. Calculate the amount in mol of carbon atoms in the students pencil lead assuming its pure graphite
0.0268
A 0.11g sample of pure barium was added to 100cm3 of water. Show that 8.0 x 10-4 mol of Ba were added to the water (Ba +2H2o -> Ba(OH)2 +H2)
0.11/137.3
Explain what is meant by a covalent bond
A shared pair of electrons
A student discovered that sea water contained chloride ions. The student added aqueous silver nitrate to a sample. What would the student see?
A white precipitate
Explain how the hydroxide ion in aqueous calcium hydroxide acts as a base when it neutralises dilute nitric acid
Accepts a proton
Write an ionic equation, including state symbols, for the reaction that would occur when a student added silver nitrate to a sample of sea water with chloride ions in it
Ag+ (aq) + Cl- (aq) --> AgCl (s)
Explain why Halogens show this trend in boiling points (an increase down the group)
As you go down the group van der waals forces increase as the number of electrons increase so more energy is needed to break the van der waals
Explain the difference between first ionisation energies of Li and Na
Atomic radii increases as there are more shells so there is more shielding and the nuclear attraction decreases which requires more energy to remove an electron from Na
State what is meant by the term isotopes
Atoms of the same element with different number of neutrons
Predict the formula of: Barium Oxide and Barium Nitride
BaO Ba3N2
One form of naturally occurring carbon is graphite. Describe the bonding and structure in graphite and explain in terms of bonding and structure, the properties of graphite shown
Bonding in graphite is a giant covalent lattice with layer of carbon atoms. Graphite is a good conductor because it has mobile electrons. It has a high melting point because covalent bonds have to be broken. Its soft because there are weak forces between the layers
State the formula of the Calcium compound formed when: calcium oxide reacts with water and calcium oxide reacts with nitric acid
Ca(OH)2 Ca(NO3)2
Write an equation including state symbols for the thermal decomposition of CaCO3
CaCO3 -> CaO + CO2
Cl2(g) + H2O(l) -> HCl(aq) + HClO(aq) State the oxidation number in Cl2? HCl? HClO?
Cl = 0 HCl = -1 and HClO = +1
Chlorine reacts with sodium hydroxide to form bleach in another disproportionation reaction. Write an equation for this reaction
Cl2 + 2NaOH -> NaClO + NaCl + H2O
Explain the difference in melting points for Sulfur (S8) and Chlorine (Cl2)
Cl2 has van der waals forces. S8 has stronger intermolecular forces than Cl2. S8 has more electrons
Contruct an equation for the decomposition of ClO2
ClO2 -> (1/2)Cl2 +O2
What term is used to describe a redox reaction in which an element is both oxidised and reduced
Disproportionation
State what is meant by the term ionic bond
Electrostatic attraction between oppositely charged ions
How is the atom of 151 Eu different from an atom of 153 Eu in terms of protons, neutrons and electrons?
Eu has 2 more neutrons
Describe what you would see when magnesium is added to an excess of hydrochloric acid dilute
Fizzing and Mg will dissolve
Work out the empirical formula of Chloric(V) acid with H-1.2% Cl-42.0% O-56.8%
HClO3
Explain the intermolecular forces in H2O that lead to a relatively high boiling point of H2O
Hydrogen bonding with a labelled diagram H-O-H ----- O-H H
The reaction with chlorine is a disproportionation reaction. Use the oxidation numbers to explain why
It has been both oxidised and reduced. It has been oxidised from 0-(+1) and reduced from 0-(-1)
Suggest one possible hazard of adding chlorine to drinking water
It is toxic
State one benefit of adding chlorine to water
Kills microorganisms
Describe and explain one anomalous property of water which results from hydrogen bonding
Liquid H2O is denser than solid as ice has an open lattice. H2O has a relatively high boiling point as the hydrogen bonds are strong
Epsom salts are crystals of hydrated MgSO4•xH20. A sample was heated to remove the water. 1.57g of water was removed leaving behind 1.51g of anhydrous MgSO4. Calculate in mol the amount of anhydrous MgSO4 formed
M(MgSO4)=120.4 Mol MgSO4 = 1.51/120.4 =0.0125 mol
Explain the difference in melting point for the elements Na and Mg
Magnesium ions have a greater charge. Magnesium has more delocalised electrons. Magnesium has a greater attraction between ions and electrons and has stronger metallic bonds
State which block the element is in: the 7th element in the 4th period
Manganese in the d block
Define the term relative isotopic mass
Mass of the isotope compared to 1/12th of the mass of carbon 12
Explain with the aid of a diagram what is meant by the term metallic bonding
Metallic bonding has electrostatic attraction between the electrons and the positive ions
Use oxidation numbers to identify which element has been oxidised (Mg + H2SO4 -> MgSO4 + H2) Explain answer
Mg as the oxidation number changes from 0-(+2)
Describe the structure and bonding shown by chlorine and magnesium
Mg has a giant structure, it has metallic bonding with positive ions and delocalised electrons. There is an electrostatic attraction between positive ions and electrons. Cl has a simple molecular lattice. Cl has instantaneous dipole induced dipoles.
Suggest the formula of sodium chlorate (VII)
NaClO4
Explain the decrease in atomic radii across the period from Na to Cl
Nuclear charge increases as electrons are added to the same shell. Electron shielding remains the same but there is a greater pull so the electrons are held in mor tightly therefore decreasing the atomic radii
Write an equation to represent the second ionisation energy of Oxygen. Include state symbols
O+(g) -> O2+(g) + e-
Explain why first ionisation energies show a general increase from Li to Ne
Outer electrons are closer to the nucleus and the atomic radii decreases. the nuclear charge increases as protons increase. Electrons are added to the same shell and shielding is similar therefore requiring more energy
Describe and explain the trend, down the group, in the reactivity of the Group 2 elements with water
Reactivity of water increases down the group. This is because atomic radii increases as there are more shells. There is more shielding. The nuclear attraction decreases which makes ot easier to remove outer electrons.
Isotopes of carbon have the same chemical properties. Explain why?
Same number of electrons in the outer shell
Compare and explain the electrical conductivities of sodium and sodium oxide in the solid and liquid states
Sodium is a good conductor because it has mobile electrons. Sodium oxide does not conduct as a solid, it only conducts as a liquid. This is because ions cannot move in a solid but ions can move when liquid
Suggest why the volume of hydrogen produced would be slighty less than the volume collected using pure Barium
Some Barium would have already reacted and there would be less Barium to react
State the shape of, and the bond angle in an NH4+ ion
Tetrahedral with an angle of 109.5
Why is Calcium nitrate an example of a salt
The H+ ion in nitric acid has been replaced by a metal ion or a Ca2+ ion
Describe what you would see when Magnesium reacts with an excess of sulfuric acid
The Magnesium dissolves and there will be gas produced
Suggest why the second ionisation energy of oxygen has a greater value then the first ionisation energy of oxygen
The electron repulsion is smaller
Define the term first ionisation energy
The energy required to remove one electron of an element from each atom in one mole of gaseous atoms to form one mole of gaseous 1+ ions
A student investigated the conductivity of ammonium chloride. She noticed that when the ammonium chloride was solid it did not conduct electricity. However, when the ammonium chloride was dissolved in water the resulting solution conducted electricity. Explain these observations
The ions cannot move in a solid whereas the ions can move in a solution
State what is meant by the term atomic number
The number of protons in the nucleus
What does (V) represent in Chloric(V) acid?
The oxidation number of chlorine
After carrying out a test the student added dilute aqueous ammonia to the mixture. What would the student see?
The precipitate dissolves
Name the shape of an ammonia molecule. And explain why the ammonia molecule has a bond angle of 107
The shape of an ammonia molecule is pyramidal. This is because there are 3 bond pairs and 1 lone pair. The lone pairs repel more than bond pairs
What term is given to '•H2O'
The waters of crystallisation
Define the term relative atomic mass
The weighted mean mass of an atom relative to 1/12th of the mass of one atom of Carbon 12
Suggest why H2S has a much lower boiling point than H2O
There are weak intermolecular forces
Why does the modern Periodic table not arrange some elements in order of increasing mass
They are arranged in increasing atomic number and properties would not be shown
Explain what is meant by the term salt
When the H+ in an acid is replaced by a metal ion or a + ion
Explain why Xenon has a lower first ionisation energy than Neon
Xenon has a bigger atomic radius as it has more shells. Xe has more shielding, the nuclear attraction decreases but the increased shielding out weighs the increased nuclear charge
