Topic 1 Flashcards
Which of the following ionisations requires a greater amount of energy than that for the process Mg(g) –> Mg+(g)?
a) Al(g) –> Al+(g)
b) Ba(g) –> Ba+(g)
c) Mg+(g) –> Mg2+(g)
d) Na(g) –> Na+(g)
C
Ions which under the same conditions, would be deflected in a mass spectrometer by the same amount as 12C2+ include
a) 12C+
b) 6Li+
c) 14N2+
d) 13C2+
b
The measured relative atomic mass of oxygen is 16.5 in a particular sample.
Which one of the following statements is not correct?
a) each atom of oxygen contains eight protons
b) the relative molecular mass of the sample is 33.0
c) there are at least two isotopes of oxygen in this sample
d) the mass spectrum of this sample shows a peak for the O+ ion at m/z = 16.5
d
In a mass spectrometer the isotopes of an element are separated and two measurements are made for each isotope
Which two measurements are made for each isotope?
m/z
relative abundance
Why is a mass spectrometer incapable of distinguishing between the ions 14N+ and 14N2 2+?
same m/z
Explain why the values shown on the graph go down from magnesium to
aluminum, and then rise again going from aluminum to silicon.
Mg –> Al
Electron removed from Al is from a higher energy level (3p rather than 3s)
Al –> Si
Si has one more proton than Al and has greater nuclear charge. The electrons removed in both cases are 3p
Electron removed from Si is closer to nucleus (than Al)
Complete the sketch graph for the elements from phosphorus to argon.
Explain why one of these elements does not follow the general trend
S does not follow trend
S has one (3)p orbital which has two paired electrons and is fully occupied
A paired electron is easier to remove
Sodium and magnesium are both in Period 3. In sodium iodide, the ions are not
polarized but in magnesium iodide some polarization occurs.
Explain the term polarization as it applies to magnesium iodide, and state
how it arises.
I- anion becomes distorted and is not spherical
Therefore Mg2+ has higher charge and a smaller radius
Bonding in magnesium iodide has some covalent character
State how thermochemical data could be used to show that there is polarization in magnesium iodide
Born Haber cycle and theoretical calculated lattice energies are different
In the context of the Periodic Table, explain what is meant by the term
periodicity
A repeating trend across a period /across each period
Name one of the elements that is composed of simple molecules at
room temperature and pressure
Phosphorus or Sulfur or Chlorine
Explain why the melting temperature of magnesium is higher than that of
sodium
Mg2+ ions are smaller than Na+ ions
magnesium has more delocalised electrons (than sodium)
more (heat) energy is needed to break the metallic bonds in Mg than in Na
What are the 2nd and 3rd stages of mass spectrometry
acceleration
deflection
Explain why a potassium ion is smaller than a potassium atom
Electrons in the ion are held more tightly
So there is less repulsion between remaining electrons
Which type of metals have the lowest ionisation energies
alkaline metals
Nuclear power stations are often proposed as suitable alternatives to those
burning coal, gas or oil.
Suggest a country where, because of its location, the dangers of nuclear power may outweigh the advantages. Justify your answer
Italy with volcanoes
Suggest the formulae of the hydrides of arsenic and selenium
AsH3 / H3As
H2Se / SeH2
Explain why the first ionization energy of selenium is lower than that of
arsenic
In Se, (spin) pairing has occurred (for the first time in that p sub-shell)
There is then an increase in repulsion so electrons are lost more easily
Explain why the first ionization energy of krypton is higher than that of selenium
The nuclear charge is increasing
electron is removed from the same sub shell
Explain why the first ionization energy of rubidium is lower than that of krypton
Rb outer electron is in another shell further from nucleus
Which of the elements, arsenic to rubidium, is likely to have atoms with the
smallest atomic radius?
Kr
Explain why the first ionization energy of the elements down Group 1 decreases even though the atomic number increases
Atomic radius increases and there is more shielding
Explain why the successive ionization energies in sodium increase
effective nuclear charge increases
Explain why, in moving from Na to Ar, the general trend is for the first ionization
energy to increase
atomic number increases
Shielding of the nucleus is about the same
Distance from nucleus is less
Estimate the value of the first ionization energy of potassium,
200 – 490
What is the structure and bonding in
Na
Si
S
giant and metallic
giant and covalent
simple and covalent
Explain why silicon has a much higher melting temperature than sulfur.
Si : covalent bonds
S : weak force e.g London forces
Explain why the melting temperature increases from sodium to aluminium
Cations/ions decrease in size, so attraction between cations and delocalised electrons increases
Magnesium forms the basic oxide magnesium oxide, MgO. This oxide is almost
insoluble in water. On gentle warming with dilute sulfuric acid, magnesium oxide reacts to form aqueous magnesium sulfate solution.
Describe how you would use the above reaction to prepare a pure sample of
magnesium sulfate.
Add MgO to acid Filter Heat/boil filtrate leave to crystallise Leave to dry
Suggest what action should be taken if a pupil spilt a small quantity of dilute
sulfuric acid on a laboratory bench
Rinse with plenty of water
Strontium sulfate is produced when aqueous sodium sulfate is added to aqueous strontium chloride.
Give the ionic equation for the reaction, including state symbols
Sr2+(aq) + SO4 2−(aq)→ SrSO4(s)
State what would be seen when concentrated sulphuric acid is added to separate solid samples of each of these compounds.
a) Lithium Chloride
b) Sodium Bromide
c) Potassium Iodide
a) white fumes
b) brown vapour
c) purple vapour
Write an equation for the reaction between concentrated sulfuric acid and solid lithium chloride
Include state symbols
LiCl2(s) + H2SO4(l) –> HCl(s) + LiHSO4(g)
When sodium chlorate(1), NaClO, is heated, sodium chlorate (V) and sodium chloride are formed
a) write an ionic equation for this
b) what type of reaction is this
a) 3OCl- –> ClO3- + 2Cl-
b) disproportionate
2IO3 +5SO2 + 4H20 –> I2 +8H+ (5SO4)2-
Has SO2 been oxidised or reduced?
Oxidised because Sulfur has lost electrons
Name a reagent that could be used to identify if a solution contains Iodine and what state would be seen
Starch
Blue/ black
How would you confirm that a solution supposedly being HCl contained chloride ions
Add dilute silver nitrate acid
White precipitate formed
Soluble in dilute ammonia
Hydrogen chloride is soluble in water. Explain why the solution is acidic.
Dissociates forming H+ ions which makes the solution acidic
Give a chemical test for chlorine stating what you’ll see and what you’d do
Bleach damp litmus paper
Sodium Iodide react with concentrated sulphuric acid to give iodine, not hydrogen iodide.
Explain why iodides react differently compared to chlorides in this situation
Iodide is more easily oxidised than HCl because it’s larger than Chlorine
2H2SO4 + 2NaBr –> Br2 + SO2 +2H2O + Na2SO4
a) Write the oxidation numbers at the start and end of the reaction for sulfur and bromine
b) Explain why the numbers in the balanced equation are consistent with the changes in oxidation number
Sulfur initially 6+ goes to +4
Bromine initally -1 goes to 0
b) An increase in Br oxidation number = 2 x 1/2
One S decreases in oxidation number by 2
HCl- 188 boiling point
HBr- 206 boiling point
HI- 238 boiling point
Explain the trend in the boiling points of the hydrogen halides
Going down the group, the number of electrons increases
So Van der Waals forces between molecules increases
Predict a value for the bp of HF and explain your reason for this
200-300 K
Hydrogen bonding is present which is a stronger intermolecular force between molecules
Define reduction in terms of changing oxidation numbers
Decrease in oxidation number
Balance the equation of sodium bromide with concentrated sulfuric acid
2NaBr + H2SO4 –> NaHSO4 + SO2 + Br2 + H2O
2NaBr + 3H2SO4 –> 2NaHSO4 + SO2 + Br2 + 2H2O
2NaBr + 3H2SO4 –> 2NaHSO4 + SO2 + Br2 + 2H2O
Use the changes in oxidation number of sulfur to show that the halides become more powerful reducing agents as the groups are descended
Change in oxidation number of S increases down the halides group
S 6+ –> 4+
Complete an equation for the hydrolysis of bromine with water which is a disproportionation reaction
Br2(aq) + H2O(I) 2H+(aq) + Br-(aq) + BrO-(aq)
Explain using oxidation numbers, why the reaction: Br2(aq) + H2O(I) 2H+(aq) + Br-(aq) + BrO-(aq) is known as disproportionation
Bromine has been both oxidised and reduced
From 0 to +1 and -1
Write the ionic equation for the reaction of chlorine gas with bromide ions
Cl2(g) + 2Br-(aq) –> 2Cl-(aq) + Br2(aq)
Balance the equation
Br2 + H2O + SO2 –> H+ + Br- + (SO4)2-
Br2 + 2H2O + SO2 –> 4H+ + 2Br- + (SO4)2-
State a fault that may occur in a procedure and recording of measurements when doing a titration
Only doing 1 titration
Not reading to 0.05cm3
State and explain the type of reaction that occurs when chlorine attacks a metal, using the example of iron
Redox reaction as chlorine removes/gains electrons from the metal and the metal gives/loses electrons to the chlorine
Suggest a reason why the use of chlorine is undesirable in swimming pools
Chlorine is highly toxic
Give the formula for calcium chlorate (1)
Ca(ClO)2
Discuss and explain the science community’s advice that CFC’s should no longer be used in aerosols, foams and refrigerants. Support your answer with one or more equations
CFC are greenhouse gases
because their dipole moment changes when they vibrate
and so contribute to global warming
depletion of the ozone later which causes less ozone to absorb UV radiation which causes skin cancer
Cl. + O3 –> ClO. + O2
ClO. + O. –> Cl. + O2
Bottle C labelled magnesium carbonate contains a white powder. When heated this powder produces a colourless gas that turns limewater cloudy.
State whether this label is correct and explain your answer
Limewater turns milky therefore CO2
MgCO3 decomposes on heating to CO2 therefore the label is correct
Describe a test to show that the solid in bottle D is barium hydroxide and not magnesium hydroxide
Substance on wire in flame, goes pale green for barium, while there would be no colour for magnesium
Bottle E is clearly labelled magnesium nitrate. When a sample of the chemical is heated it gives off a brown gas and a gas that relights a glowing splint
Give the name of each of the gases formed and write an equation for this chemical reaction
Oxygen given off
NO2 given off –> brown gas
2Mg(NO3)2 –> 2MgO + 4NO2 +O2
Explain the origin of the flame colour
Electrons excited so fall to a lower energy level and give out energy in the form of light
What is meant by the term polarising power as applied to cations
The ability of cations to distort the electron cloud around an anion
Why is it easier to decompose magnesium nitrate than barium nitrate by heating
Magnesium ion is smaller than the barium ion and so has a higher change density so the polarising power increases this weakens the bonds in the nitrate
State and explain the trend in thermal stability of the carbonates of the Group 2 elements as the group is descended
Thermal stability increases as cation size increases so therefore polarises the carbonate ion
Magnesium oxide is a basic oxide which produces an alkaline solution with water. Write an equation to show how the oxide ion, O2-, acts as a base in the reaction with water
O2- +H2O –> 2OH-
Write the equations to show the action of heat on the following solid nitrates.
a) LiNO3
b) CsNO3
a) 4LiNO3 –> 2Li2O + 4NO2+O2
b) 2CsNO3 –> 2CsNO2 + O2
What difference would you expect to see after calcium metal and barium metal have reacted with water
Calcium would go cloudy but barium goes clear
The reaction between barium metal and excess dilute sulphuric acid stops after a very short time. Suggest an explanation for this
Insoluble coating of barium sulphate formed which prevents acid getting to the surface of barium
Write the ionic equation for the reaction of calcium metal with dilute hydrochloric acid
Ca(s) + 2H+(aq) –> Ca2+(aq) + H2(g)
When a small piece of barium is added to water, the barium gets smaller and eventually disappears
State TWO other observations you could make
Gets warm
Fizzing
Which concentrated acid should be used to dissolve a carbonate of a group 2 metal to carry out a flame test
a) ethanoic acid
b) hydrochloric acid
c) nitric acid
d) sulfuric acid
hydrochloric acid
What colour does a barium salt give in a flame test
a) colourless
b) green
c) red
d) yellow-red
b
Separate flame tests are carried out with lithium, sodium, potassium, magnesium, calcium and strontium salts. How many of these metal ions would colour the flame red?
C
A group 2 element reacts vigorously with water to produce a soluble hydroxide which forms a white precipitate when neutralised by sulfuric acid and forms a carbonate which is very stable to heat.
The element could be
a) magnesium
b) calcium
c) strontium
d) barium
d
The group 2 metals, considered in order of increasing atomic number show a decrease in
a) first ionisation energy
b) nuclear charge
c) chemical reactivity
d) ionic radius
a
