Physical- incorrect questions
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Give the equation for the third ionisation energy of Mg w state symbols
Mg2+(s)–>Mg3+(g)+e-
Explain why the third IE of mg is much higher than the 2nd IE of mg
M1) removing electron from p shell M2) electron removed has less shielding
Explain why CBr4 is not a polar molecule
The C-Br polar bonds cancel out because the molecule is symmetrical.
Foul smelling gas
hydrogen sulfide
Explain why using a catalyst has no effect on the percentage yield
Affects rate of forward and backward reaction equally
Why is Na2CO3 added to unknown substances
Tests to see if it’s acidic/ has H+ ions
How can you determine which element a set of ionisation energies belong to?
FInd the largest gap, eg 4th-5th Count 4 back from group 0, eg Ar-C
What is the trend in oxidising ability of group 7 elements going down the period
oxidising ability decreases
What is responsible for conducting the electricity in water molecules?
The ions
What is responsible for conducting the electricity in metal?
The bonding electrons
Suggest one reason other than incomplete combustion or heat transfer to the atmosphere why the student’s value for the enthalpy of combustion of methanol is different from the Data Book.
evaporation of the alcohol (fuel) experiment not done under standard conditions heat capacity of copper not taken into account
Platinum, palladium and rhodium are metals used inside catalytic converters. A very thin layer of the metals is used on a honeycomb ceramic support. Explain why a thin layer is used in this way.
to reduce the amount of metal needed to produce a large surface area
Sulfur dioxide (SO2) is produced when some fossil fuels are burned. How can it be removed?
Sulfur dioxide can be removed from waste gases in a power station by an acid-base reaction with calcium oxide.
Suggest one reason why, other than mean bond enthalpies, why a value for the enthalpy of combustion of a liquid alknae is different from value obtained from calculations of ΔcH
(ALKANE MOLECULES MUST BE GASEOUS IN ORDER TO COMBUST- IT DOESN’T MATTER IF THE FULE ITSELF IS LIQUID OR SOLID IT MUST BE GASEOUS TO UNDERGO COMBUSTION) M1) the alkane is not gaseous and it would takes energy to convert it to a gas
Which of these species is the best reducing agent?+ explain why Cl2 Cl- I2 I-
I- because it already has an extra electron to loose.
State which of the elements magnesium and aluminium has the lower first ionisation energy. Explain your answer.
Al (Outer) electron in (3)p sublevel/orbital Higher in energy/further from the nucleus so easier to remove
student obtained a value for the enthalpy of reaction of −142 kJ mol−1 A data book value for the enthalpy of reaction is −310 kJ mol−1 Suggest the most likely reason for the large difference between the student’s experimental value and the data book value.
Heat loss (from the apparatus would mean the experimental value is smaller/lower/less exothermic than the data source)
Ways to imporve required practical 2. Measurement of an Enthalpy Change
• Insulate the beaker or use a polystyrene cup or a lid • To reduce heat loss • Record the temperature for a suitable time before adding the metal • To establish an accurate initial temperature • Record temperature values at regular time intervals • To plot the temperature results against time on a graph • Extrapolate the cooling back to the point of addition • To establish a (theoretical) maximum temperature OR temperature change (e.g. at the 4th minute) OR adjust for the cooling /apply a cooling correction
What is the best technique to remove the silver chloride that forms when aqueous solutions of silver nitrate and sodium chloride react?
Filtration
How can titration results be lower than the actual value
rinding the burrette with distilled water before filling
Which of these has the higehst 1st ionisation energy: sodium aluminium silicone chlorine
chlorine