Bonding Werners Theory - UNSOLVED PRACTICE SET

Q7. State the two types of valencies proposed by Werner. How do they differ from each other?

Q8. According to Werner's theory, explain why [Co(NH₃)₆]Cl₃ gives three chloride ions upon ionization, while [Co(NH₃)₅Cl]Cl₂ gives only two.

Q9. What is the coordination number of cobalt in Werner's complexes? How did Werner determine it experimentally?

Q10. Distinguish between primary valency and secondary valency in terms of (a) ionizability and (b) directionality.

Q11. Why did Werner's theory mark a turning point in the understanding of coordination compounds?

Q12. According to Werner, what is the shape of the coordination entity when the coordination number is 6? What is the shape when the coordination number is 4?

Q13. State and explain Werner's theory of coordination compounds. What are the postulates of this theory? How did Werner explain the structure of [Co(NH₃)₆]Cl₃ using his theory?

Q14. (a) Explain how Werner's theory accounts for the following experimental observations:

(i) [Co(NH₃)₆]Cl₃ conducts electricity and gives 3 moles of AgCl with AgNO₃

(ii) [Co(NH₃)₅Cl]Cl₂ conducts electricity and gives 2 moles of AgCl with AgNO₃

(iii) [Co(NH₃)₄Cl₂]Cl conducts electricity and gives 1 mole of AgCl with AgNO₃

(iv) [Co(NH₃)₃Cl₃] does not conduct electricity and gives no AgCl with AgNO₃

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(b) What do these observations tell us about the nature of primary and secondary valencies?

Q15. (a) How did Werner's theory explain the existence of isomers in coordination compounds? Give an example.

(b) What were the limitations of Werner's theory? (List at least two.)

Q16. A series of cobalt(III) complexes were studied by Werner:

Complex 1: [Co(NH₃)₆]Cl₃ — molar conductance = 430 ohm⁻¹ cm² mol⁻¹

Complex 2: [Co(NH₃)₅Cl]Cl₂ — molar conductance = 290 ohm⁻¹ cm² mol⁻¹

Complex 3: [Co(NH₃)₄Cl₂]Cl — molar conductance = 145 ohm⁻¹ cm² mol⁻¹

Complex 4: [Co(NH₃)₃Cl₃] — molar conductance = 0 ohm⁻¹ cm² mol⁻¹

(a) Explain the trend in molar conductance values using Werner's theory.

(b) Predict how many ions each complex would produce in solution.

(c) How many moles of AgCl would precipitate per mole of each complex when treated with excess AgNO₃?

(d) Which complex(es) would be electrolytes and which would be non-electrolytes?

Q17. Werner studied a compound with the formula PtCl₄·2NH₃. He found that:

It does not conduct electricity in solution

All four chloride ions are present in the coordination sphere

It exists in two isomeric forms

(a) Write the coordination formula of the compound according to Werner's theory.

(b) Draw the two isomeric forms.

(c) What type of isomerism is shown? Name the isomers.

(d) Explain why this compound does not conduct electricity.

(e) How does this compound support Werner's idea about the difference between primary and secondary valencies?

Q18. In a classroom activity, your teacher demonstrates the conductivity of different cobalt(III) complexes using a simple conductivity apparatus with a battery and bulb.

(a) The bulb glows brightly with [Co(NH₃)₆]Cl₃ solution, less brightly with [Co(NH₃)₅Cl]Cl₂, dimly with [Co(NH₃)₄Cl₂]Cl, and not at all with [Co(NH₃)₃Cl₃]. Explain these observations using Werner's theory.

(b) When AgNO₃ is added to each solution, white precipitates form in different amounts. Predict the number of moles of AgCl formed per mole of each complex.

(c) The teacher asks: "If I replace NH₃ with H₂O in these complexes, would the conductivity pattern remain the same?" What would be your answer and reasoning?

(d) How did Werner's experimental approach (conductivity + precipitation) revolutionize the understanding of chemical bonding in coordination compounds?