1The hydration of anhydrous copper(II) sulfate is reversible
CuSO4(s) + 5H2O(l)<--> CuSO4.5H2O(s)
The forward reaction is exothermic. The temprature changes for both the forward and reverse reactions are difficult to measure
Suggest a reason in each case
Forward: the temprature of a solid is difficult to measure
reverse: the salt may decompose further
2 Why do some ionic compounds dissolve in water?
-Hydration enthalpy is greater than the bond (lattice) enthalpy.
-Greater energy is released during the formation of ion-dipole bonds with water than is required to break the ionic bonds.
3NH2CONH2(s) + H2O(l)<---> 2NH3(g) + CO2(g)
The ammonia formed may escape into the atmosphere unless it dissolves in water. Crops cannot absorb ammonia or urea directly but can take up and use dissolved ammonium ions
suggest why urea is used as a feriliser for crops such as rice but not in regions with unpredictable rainfall patterns.9
- It's used for crops such as rice because the ammonia produced will dissolve in water and not be lost
- in areas of unpredictable rainfall the urea will breakdown and the ammonia will vapourise
4Give 2 reasons whys it's important to remove nitrogen oxides from the exhaust gases of diesel engines
- oxides of nitrogen dissolve in water to form acid rain
-oxides of nitrogen cause breathing problems
5The student's value were different from data book value. Student A's value (calorimetry method)
AgNO3(aq) + 0.5 Zn(s)---> 0.5 Zn(NO3)2(aq) + Ag(s) delta = -36.1kj
was lower and student B's value (gravimetric method) was higher.
AgNO3(aq) + KBr(aq)---> AgBr(s) + KNO3(aq)
Give a possible reason for each
- the calorimetry methods is lower because heat may be lost to the surrounding
- the gravimetric method is higher because the product may have impurities
6Show the products of the oxidation of methanol to methanoic acid
CH3OH + 2[O] ---> HCOOH + H2O
7Give a chemical test, and it's positive result, that could be used to confirm the functional group in methanoic acid
- add sodium hydrogen carbonate
-Dissaperance of the solid sodium hydrogen carbonate
- bubbles given off
8Methanol produced from petrol by CCU may be mixed with petrol derived from fossil fuels. A concentration of 5% by mass of methanol is used.
Explain how the use of this fuel would affect the increase in global tempratures.
-Burning methanol produces CO2 whih is a greenhouse gas
-methanol is made from captured CO2
9Give the systematic name of KClO4
Pottasium chlorate (VII)
10What would be seen in the reaction of pottasium iodide with concentrated sulfuric acid
Misty fumes (iodine vapour)
Black solid (iodine)
Yellow solid (sulfur )
11give the meaning of the term "mean bond enthalpy"
-the energy required to break one mole of a bond
- in the gaseous state
12How would including the heat capacity of the calorimeter affect the calculated enthalpy change of a reaction?
-The calculated enthalpy change would be greater (more exothermic),
-because more heat is accounted for — including the energy absorbed by the calorimeter itself, not just the solution.
13Suggest suitable reagents and conditions for the conversion of propene to propane-1,2-diol.
Reagent: Cold, dilute acidified potassium manganate(VII) (KMnO₄) (converts alkenes to diol)
Conditions: Cold and dilute solution, typically in dilute sulfuric acid (H₂SO₄)