Periodic Classification of Elements — Science STD 10 — Question

On adding dilute hydrochloric acid to copper oxide powder, the solution formed is blue-green.

1. Predict the new compound formed which imparts a blue-green colour to solution.
2. Write a balanced chemical equation of the reaction which takes place.
3. On the basis of the above reaction, what can you say about the nature of copper oxide?

State some of the uses of mineral acids in industry.

State any three limitations of Mendeleev’s classification of elements.

Name three products of the chlor-alkali process. State two uses of each of these products.

Explain why, a solution of cane sugar does not conduct electricity but a solution of common salt is a good conductor of electricity.

Based on the group valency of elements write the molecular formula of the following compounds giving justification for each:

1. Oxide of first group elements.
2. Halide of the elements of group thirteen.
3. Compound formed when an element, A of group 2 combines with an element, B of group seventeen.

What is meant by strong bases and weak bases? Classify the following into strong bases and weak bases:
NH₄OH, Ca(OH)₂, NaOH, KOH, Mg(OH)₂

Generally, when metals are treated with mineral acids, hydrogen gas is liberated but when metals (except Mn and Mg), treated with HNO₃, hydrogen is not liberated, why?

When a green iron salt is heated strongly, its colour finally changes to brown and odour of burning sulphur is given out:

1. Name the iron salt.
2. Name the type of reaction that takes place during the heating of iron salt.
3. Write a chemical equation for the reaction involved.