O Level | IP Chemistry Tuition – Are you able to answer this Secondary Chemistry Tuition Question?

09 May O Level | IP Chemistry Tuition – Are you able to answer this Secondary Chemistry Tuition Question?

5 .        Boron nitride, BN, exists in two physical forms. The structures of these forms are shown below.

chemistry_tuition_q

These two forms of boron nitride resemble two allotropes of carbon.

 

(a)        Suggest why boron nitride with structure A can be used as a lubricant.

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(b)        Suggest why boron nitride with structure B does not conduct electricity.

 

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(c)        Suggest why boron nitride with structure B can be used in cutting tools and drill bits.

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  1. An impure sample of iron(II) sulphate was analysed by titration.

 

The sample was dissolved in 25.0 cm3 of dilute sulphuric acid and then titrated against 0.0400 mol/dm3 potassium dichromate(VI) solution.

 

19.0 cm3 of potassium dichromate(VI) solution was required to reach the end-point.

 

(a)        Calculate the number of moles of potassium dichromate(VI) used in the titration.

…………………………………. moles

 

 

(b)        One mole of potassium dichromate(VI) reacts with six moles of iron(II) ions.

Calculate the mass, in grams, of iron(II) ions in the sample analysed.

 

mass of iron(II) ions…………………………………. g

 

 

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Did you answer the Secondary Chemistry Tuition Question correctly?

 

5.a. Soft / slide pass each other

 

  1. No mobile electrons / ions

 

  1. All atoms are strongly held together by covalent bonds, compact & closely packed, bonds between atoms are difficult to be broken

 

6.a. 0.00076 mol

 

  1. 0.255 g (3s.f.)

 

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