Spec points I don’t know very well

Explain why values from mean bond enthalpy calculations differ from those determined using Hess’s law

They are not exact and vary in each situation, data book values are averaged across lots of compounds

How many electron pairs does oxygen have?

2 electron pairs

What are the benefits of high atom economy?

• means little/no waste product, only desired product - economically viable

• uses less natural resources and often less energy - more beneficial for environment

What is the shape of the graph for lnk against 1/T? (Linked to Arrhenius)

• the graph is a negative gradient straight line

• \

• (Know it will be negative because gradient is -Ea/R)

What are the simplified positive and negative electrode reactions in a lithium cell?

Positive electrode:

Li+ + CoO2 + e- —> Li[CoO2]-

Negative electrode:

Li —> Li+ + e-

What are the electrode reactions in an alkaline hydrogen-oxygen fuel cell?

E right (+ive electrode):

4e- + 2H2O + O2 —> 4OH-

E left:

2H2 + 4OH- —> 4H2O + 4e-

pKa=

-log(10)Ka

How can you calculate the Ka of a weak acid with a graph?

Measure the pH at half neutralisation

What is the equation for the use of magnesium in the extraction of titanium from TiCl4?

TiCl4 + 2Mg —> 2MgCl2 + Ti

What is the equation for the use of CaO to remove SO2 from flue gases?

CaO + 2H2O + SO2 —> CaSO3 + 2H2O

Acidified BaCl2 solution can be used to test for sulfate ions. Why is it acidified?

Adding dilute acid first removes any carbonate impurities that may be present and would give a false positive result for sulfates

What is the most electronegative element?

Fluorine

What is the equation(s) for the reaction of solid sodium fluoride with concentrated sulfuric acid?

NaF + H2SO4 —> NaHSO4 + HF

What is the equation(s) for the reaction of solid sodium chloride with concentrated sulfuric acid?

NaCl + H2SO4 —> NaHSO4 + HCl

What is the equation(s) for the reaction of solid sodium bromide with concentrated sulfuric acid?

• NaBr + H2SO4 —> NaHSO4 + HBr

• 2HBr + H2SO4 —> Br2 + SO2 + 2H2O

What is the equation(s) for the reaction of solid sodium iodide with concentrated sulfuric acid?

• NaI + H2SO4 —> NaHSO4 + HI

• 2HI + H2SO4 —> I2 + SO2 + 2H2O

• 6HI + SO2 —> H2S + 3I2 + 2H2O

What are the equations for the 2 reactions of chlorine with water?

With cold water:

Cl2 + H2O —> ClO- + Cl- + 2H+

(Forms chloride and chlorate ions)

With UV light:

2Cl2 + 2H2O —UV—> 4HCl + O2

What is the equation for the reaction of chlorine with cold, dilute, aqueous NaOH?

2NaOH + Cl2 —> NaClO + NaCl + H2

What is the test and results for group 2 ions?

Flame test

• calcium ions (Ca2+) is brick red

• strontium ions (Sr2+) is red

• barium ions (Ba2+) is pale green

What is the test and results for ammonium (NH4+) ions?

Red litmus paper turns blue

(Because ammonia gas is given off which is a base)

What is the test for group 7 (halides)?

• acidified silver nitrate

• then dilute then conc ammonia

What is the test and result for OH- ions?

Red litmus paper turns blue

What is the test and result for CO3 2- ions?

• add an acid

• effervescence, and CO2 given off

• the CO2 gas can be bubbled through limewater, turns it cloudy

What is the test and results for SO4 2- ions?

Use BaCl2, forms white precipitate

What are the equations for the reaction of Na and Mg with water?

• 2Na + 2H2O —> 2NaOH + H2

• Mg + 2H2O —> Mg(OH)2 + H2

Reaction with Mg is slow, can be made faster by using steam

• Mg + H2O(g) —> MgO(s) + H2

Aluminium oxide is amphoteric. Give equations for it reacting with an acid and an alkali

• Al2O3 + 3H2SO4 —> Al2(SO4)3 + 3H2O

• Al2O3 + 2NaOH —> 2NaAl(OH)4