Exp Reactants Products Observation

I2.6 g of zinc and 50 cm3 of acid P

2.0 mol dm-3

Zinc chloride and hydrogen

gas

The temperature

of the mixture increases

II2.6 g of zinc and 50 cm3 of acid Q

2.0 mol dm-3

Zinc sulphate and hydrogen

gas

The temperature

of the mixture increases

data from Exp I and Exp II that were carried out to study the rate of reaction of zinc with two acids, P and Q.

QUESTION 1- RATE OF REACTION

• (i) By choosing either Experiment I or Experiment II, state the name of the acid used.

•  

• (i) Write the chemical equation for the reaction of this acid with zinc. [2 marks]

(ii) Draw an energy profile diagram for the reaction in 10(a)(i). On the energy profile diagram show the:–Heat of reaction, AH–Activation energy without a catalyst, –Activation energy with a catalyst, E'

Explain the energy profile diagram.[10 marks]

∆H

E- activattion energy without catalyst

E’- activattion energy with catalyst

energy

Energy profile diagram of reaction zinc and hydrochloric acid

(ii) Explain the energy profile diagram.

∆H

(ii) Explain the energy profile diagram.

∆H

(ii) Explain the energy profile diagram.

∆H

∆H

(ii) Explain the energy profile diagram.

∆H

(ii) Explain the energy profile diagram.

∆H

What is the function of these food additives?

a) Colouring agents

b) preservatives

c) Anti oxidants

d) Flavouring agents

e) Stabilisers and thickeners

a) To restore the colour of original food

b) To destroy or prevent growth of micro organisms in food

c) To prevention oxidation of food by air

d) To to give or enhance the flavour of food

e) To prevent food such as ice cream from separating into layers

and to thicken soup or gravy

Question no. 2) consumer

What type of food additives?

Colouring agents

preservatives

Anti oxidants

Flavouring agents

Stabilisers and thickeners

a) Benzoic acid

b) Pectin

c) Saccharin

d) aspartam

e) Ascorbic acid

Flavouring agents

f) tartrazine

f) Sodium nitrite preservatives

What type of food additives?

Colouring agents

preservatives

Anti oxidants

Stabilisers and thickeners

a) Azo compound

b) Vitamin E

c) Mono sodium glutamate

d) agar-agar

e) Gelatin

Flavouring agents

f) Sodium benzoate

Stabilisers and thickeners

g) Sulphur dioxide preservatives

What is the function of these traditional medicines?

a) lime

b) garlic

c) ginger

d) onions

e) Betel leaves- daun sireh

a) To increase digestive juice

b) Has antibiotic property

c) To warm the body

d) To purift blood

e) Stop bleeding nose

What is the function of these modern medicines?

a) analgesics

b) antibiotics

c) Psychotherapeutic

medicines

a) To relieve pain without affecting consciousness

b) Kill bacteria

c) To treat mental illness

a) stimulants

b) Antidepressant

c) Antipsychotic drug

a) To stimulate mental activity

b) To control worry, fear, anxiety, panic

c) To treat psychotic illness or

schizophrenia

c) Psychotherapeutic medicines

What type of modern medicines?

analgesics

Anti biotics

a) aspirin

b) Penicillin

c) streptomycin

d) Para cetamol

e) caffeinef) codeine

g) barbiturate

Anti biotics

analgesics

stimulantanalgesics

antidepressant

h) tranquiliser antidepressant

What is the uses of modern medicines?

Fever, prevent heart attack

fever

a) aspirin

b) Penicillin

c) streptomycin

d) Para cetamol

f) codeine

pneumonia Tuberculosis, dysentry

Treat gonorrhea, syphlis, pneumonia, meningitis

Cough medicine, headache

Soap:RCOO – Na + or R COO – K +

Detergent:

What is general formula for soap?and detergent?

What does hard water contains?

• Hard water contains calcium ion, Ca2+ or magnesium ion, Mg2+.

Why do soaps form scum with hard water?

• Soap reacts with calcium ion, Ca2+ or magnesium ion, Mg2+ in hard water to form insoluble salt, called scum

Why is soap not effective in hard water?

• Because formation of scum reduce the amount of soap for cleaning and thus wastage of soap occur.

Why is detergent more effective than soap in hard water?

 • Detergent form soluble salt with calcium ion, Ca2+ or magnesium ion, Mg2+ in hard water.

• Therefore the cleaning power is not affected by hard water.

Below are some additives in detergents. Fill in missing words

Additives Functions

1 Drying agents

( such as sodium sulphate, sodium silicate)

to keep the powder……………….DRY

Additives Functions 2 Builders

( such as Sodium triphosphate)

……………water.

soften

Additives Functions 3 Biological

enzymes

( such as amylase, lipase)

to digest

in dirt or to modify fabric feel

PROTEIN, FAT OR CARBOHYDRATE

Additives

Functions

4 Such as sodium perborate

Convert stains into

…………………substances

colourless

Additives

Functions

5  Perfumes Make clothes smell  

……………. And clean

fresh

Additives Functions 6. Stabilizers

( such as silicones)

Prevent formation of

………………

foam

Change of one homologous series to another homologous 

series 

Question 3) Revision on alcohols, carboxylic acids and ester

Alcohol 

Carboxylic acid 

Ester

State the general formula for 

Many reactions of ethanol

Reaction 1

• Combustion• ethanol is burnt in excess oxygen

Observation: ethanol burns with blue flame, no soot

Reaction 2

• Dehydration • ethanol is passed over heated   porcelain chips to produce ethene 

Observation: gas formed that will decolorize brown bromine water 

Reaction 3

• hydration or addition of steam• When a mixture of ethene and steam is heated over phosphoric acid as catalyst, temp of 300oC, pressure 60 atm. 

Reaction 4

• Esterification • When a mixture of ethanol and ethanoic acid  is warmed with conc sulphuric acid as catalyst,  Observation: sweet smelling liquid is formed

Reaction 5

• Esterification • When a mixture of ethanoic acid and ethanol is warmed with conc sulphuric acid as catalyst

Observation: Sweet smelling liquid is formed

Reaction 6

• Oxidation • When ethanol is warmed with acidified potassium dichromate as oxidizing agent

Observation:Orange solution change to green

Naming of esters

5) A student obtained the data to determine heat of precipitation of PbSO4Solution Vol

(cm3)Conc(moldm-3)

Initial temp(0C)

Pb(NO3)2 50 0.5 27.4

Na2SO4 50 0.5 27.6

Highest temperature : 30.5 0C

Question 4- thermochemistry

What is meant by heat of precipitation?

• Heat changed when 1 mole of precipitate is formed from its ions in an aqueous solution

b) Calculate heat of precipitation of PbSO4

• Mole Pb 2+ : (0.5)(50)/1000 = 0.025 mol• Mole SO4 2- :  (0.5)(50)/1000 = 0.025    

mol• Pb2+  +  SO2-4                       PbSO4 mole PbSO4 = Mole Pb2+ or  mole SO2-4 

                      = 0.025 mol

ϴ = 30.5 -  (  27.4 + 27.6 )                         2    = 3.0 ° CHeat of precipitation = mCϴ                                          mol                                    = ( 100)(4.2)(3)                                              0.025                                     = 50400 J/mol                           ∆ H = - 50.4 KJ/mol

d)Write thermo chemical equation

•Pb2+ + SO42-                        PbSO4

∆ H = - 50.4 KJ/mol

e) Write the ionic equation

•Pb2+ + SO42-                        PbSO4

E) Construct energy level diagram

                

    Pb2+ + SO42-

Energy

∆ H = - 50.4 KJ/mol

PbSO4

f) The experiment is repeated using K2SO4 to replaced Na2SO4. Heat of precipitation

of PbSO4 remain the same. Explain.

• Because the same precipitate is formed, which is PbSO4.

• Only Pb 2+ ions and SO4 2- ions react

• Na+ ions and K+ ions do not react

• 6) A student carried out an experiment to determine heat of displacement of copper from CuSO4 solution. He added excess zinc powder to 50 cm3 of 0.2 moldm-3 CuSO4. The thermo chemical equation is shown below :

Zn + Cu2+ Zn2+ + Cu ∆ H = -80.64 KJ/mol

a) Calculate the change in temperature

Mol Copper= mol copper(II) sulphate = (0.2)(50)/1000 = 0.01 mol

∆ H = mCϴ mol80 640 J = ( 50)(4.2)(ϴ) 0.01 ϴ = 3.8 ° C

b) Write the ionic equation

Zn + CuSO4 Cu + ZnSO4

Zn + Cu2+ Zn2+ + Cu

The experiment is repeated with the following changes. What is the effect in the change of temperature when :• Concentration of CuSO4 is doubled, without changing the volume :

So, change of temp or ϴ is doubled. Because as the concentration doubled, the number of particle per unit volume also doubled.

The experiment is repeated with the following changes. What is the effect in the change of temperature when :

• volume of CuSO4 is halved, without changing the concentration :

So, change of temp or ϴ is remain the same. Because, the changes in volume do not affect the number of particles per unit volume

7) State the diff betw heat change and the heat of reaction

HEAT CHANGE HEAT OF REACTION

A) OTHER NAMES

Depends on name of reactions :

Heat absorb, heat

released

-Heat of Precipitation-Heat of displacement-Heat of neutralisation-Heat of combustion

7) State the differences between heat change and heat of reaction

HEAT CHANGE HEAT OF REACTION

B) FORMULA USED H= mCϴ ∆ H= mCϴ

          molC)UNIT Joule Kilo Joule/ molD) SYMBOL none ∆ HE) SIGN No sign Either + for 

endothermic rex or – for exothermic rex