Things I learnt from papers MC - QCAA, Total Education, Neap etc

Question 1

What do you do when finding the pH of an hydroxide

Answer 1

Find pH with hydrogen concentration and subtract from 14.

Question 2

How to deduce a conjugate acids of a base?

Answer 2

In a reaction where its base + water then the water acts as the acid donating one proton to the base. Hence the conjugate acid will be the base + that one proton donated by water.

Question 3

In an acid or base how to determine which one is placed in a burette or conical flask?

Answer 3

In the x-axis if it says volume of base added the base is in the burette or if is says volume of acid added the acid is in the burette. Also if you look on the titration curves if it starts at low pH (as indicated by the y-axis) then the acid is in the conical flask however if it starts on a high pH the base is in the conical flask.

Question 4

Oxidation Number Rules for Certain Elements

Answer 4

Group 1 - +1
Group 2 - +2
Fluorine - -1
Hydrogen - +1 but in hydrogen + metal it is -1
Oxygen - -2 but in peroxides like H2O2 it is -1
Ionic Compounds = charge
Covalent Compounds more electronegative has a negative oxidation state

Question 5

Why do carboxylic acids have a stronger hydrogen bonding compared to alcohols?

Answer 5

With a water molecule alcohol can only make 3 hydrogen bonds maximum with the number of lone pairs it has. However with carboxylic acid it has multiple hydrogen bonding when combined with water making it stronger than that of alcohol.

Question 6

What is esterification

Answer 6

Esterification is the formation of an ester. Made using carboxylic acid and alcohol with concentration sulfuric acid as a catalyst which will speed up the reaction considering it is a slow one.

Question 7

Carbohydrates consist of what?

Answer 7

1. Polyhydroxy (many OH- groups)
2. Ketones
3. Aldehydes

Question 7

Carbohydrates consist of what?

Answer 7

1. Polyhydroxy (many OH- groups)
2. Ketones
3. Aldehydes

Question 8

How to read an infrared spectroscopy?

Answer 8

Match the peaks closest to the x-axis to the infrared data provided in the data booklet. Using all bonds match up to the most likely compound.

Question 9

What is the difference between anaerobic and aerobic conditions

Answer 9

Anaerobic -> closed environment with no oxygen
Aerobic -> open environment with oxygen.

Question 10

Calculating Atom Economy

Answer 10

% Atom Economy = Mass of desired product/all reactants *100

Note: molar mass must be multiplied by the coefficient of the desired product or reactants.

Question 11

What affects Kc?

Answer 11

Only temperature affects Kc which is known as the position of equilibrium. However there are other factors that affect equilibrium such as pressure, concentration, temperature and catalyst.

Question 12

Reactions with Triglyceride

Answer 12

Triglyceride + 3Water -> Glycerol + 3Fatty Acid

Triglyceride + 3NaOH -> Glycerol + 3Sodium Stearate (Soap)

Triglyceride + methanol or ethanol -> Glycerol + 3methyl ester or ethyl ester

Question 13

Triglycerides are an example of what organic molecule?

Answer 13

Esters (CH2OCOR’)

Cut in between the CH2 and O

Question 14

How to determine molecular formula from a mass spectra diagram?

Answer 14

Look at the very last peak furthest along the x-axis. This is the molecular ion peak. From this we can deduce the molar mass and match it up with the proper molecular formula.

Question 15

How does the hydrogen fuel cell work?

Answer 15

Question 16

Pros and Cons of a Hydrogen Fuel Cell

Answer 16

Question 17

What is the structure of an amide?

Answer 17

An amide is R C double bond NH2. However note the NH2 is only present when the nitrogen is at the end of the carbon if in the middle due to lack of bonds it will be NH since that will show the amide link.

Question 18

Enzymes can act as a biological catalyst….

Answer 18

Because they lower the activation energy. Catalyst can be both organic and inorganic. But they have the same purpose of lowering the activation energy.

Question 19

Calculating Percentage Yield

Answer 19

This formula is on the chemistry QCAA data booklet. It is actual/theoretical *100%. In order to calculate the theoretical yield you must find the limiting reagent and put a ratio between the limiting reagent and what is in excess. This way you can calculate how many moles is actually used up. Then substitute this into the formula or calculate the molar mass if required then substitute it into the formula.

Question 20

What is the product when alkene reactions with water?

Answer 20

Alcohol. This is a hydration reaction as per the reaction pathways.

Question 21

Why is a catalyst needed when producing ethanol through the fermentation of glucose?

Answer 21

Because a catalyst lowers the activation energy so that less energy is required for the reaction. This then increases the rate of reaction.