Miracle Learning Centre (O Level Chemistry Tuition/ IP Chemistry Tuition) Are you able to answer this Secondary Chemistry Tuition Question?

22 May Miracle Learning Centre (O Level Chemistry Tuition/ IP Chemistry Tuition) Are you able to answer this Secondary Chemistry Tuition Question?

7) Aqueous hydrogen peroxide is used to sterilise contact lenses. At room temperature, aqueous hydrogen peroxide decomposes very slowly to form water and oxygen.

The decomposition can be represented by the equation below:

2  H – O – O – H     O = O   +  2 H – O – H       ∆H = – 206 kJ/mol

 

a) With reference to the energy changes during bond breaking and bond formation, describe and explain how the temperature of the solution changes when aqueous hydrogen peroxide decomposes.
a) With reference to the energy changes during bond breaking and bond formation, describe and explain how the temperature of the solution changes when aqueous hydrogen peroxide decomposes.
…………………………………………………………………………………………………
…………………………………………………………………………………………………

b)

The table shows some bond energies, measured in kilojoules per mole, kJ/mol.

Bond Bond energy in kJ/mol
O – H 463
O = O 496

Use the data provided to calculate the bond energy for the O – O bond in hydrogen peroxide.

 

8)      An organic compound X has a structural formula as shown in the diagram below:

chemistry_tuition_q

  1. a) Isomers can have different functional groups.

(i)   Write the molecular formula of compound X.                                ………………

(ii)   An isomer of compound X has the condensed formula CH2CHCOOCH3.                       Draw the full structural formula of CH2CHCOOCH3.

 

  1. b) The following tests were carried out on compound X.
Test I       Compound X is shaken with aqueous bromine to give compound A.Test II     Magnesium ribbon is added to an aqueous solution of compound X.

Test III     On refluxing with a little concentrated sulfuric acid, compound X reacts with methanol to give another compound B.

 

(i)   Describe an observation made in Test I and explain your answer.

…………………………………………………………………………………………………

…………………………………………………………………………………………………

(ii)  Draw the full structural formula of compound A.

(iii) Construct a balanced chemical equation for the reaction in Test II.

…………………………………………………………………………………………………

(iv)  State one physical property of compound B.                                                     ……………………………………………………………………………………………

 

 

 

Miracle Learning Centre (O Level Chemistry Tuition/ IP Chemistry Tuition)

Did you answer the Secondary Chemistry Tuition Question correctly?

 

7.a. The temperature of the solution increased.

The energy released into the surrounding during bond making is greater than the energy absorbed during bond breaking.

  1. Energy absorbed to break 4 O – H bonds and 2 O – O bonds

= 4(+463) + 2x

Energy released to form 1 O = O bond and 4 O – H bonds

= -496 + 4(-463)

4(+463) + 2x + (-496) + 4(-463) = -206

                                                x = 145

O – O bond energy = 145 kJ/mol

8.a.i. C4H6O2

chemistry_tuition_q

b.i. Reddish-brown solution of bromine decolourises/ turns colourless.

Compound X is an unsaturated compound / contains C=C bond which allows bromine atoms to be added

 

  1. Mg + 2 CH3COOH → Mg(CH3COO)2 + H2chemistry_tuition_qLearn from our Chemistry Tuition Question and Answer.Miracle Learning Centre Call 6463 8756 or sms 8128 8342/9839 9908.

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