Periodic Classification of Elements — Science STD 10 — Question

How can tooth decay be prevented ?

A white powdery substance having strong smell of chlorine is used for disinfecting drinking water supply at waterworks. Identify the substance. Give its chemical name and write the chemical reaction for its preparation.

Explain why, the first period of the modern periodic table has only two elements whereas second period has eight elements.

Explain the given reaction with the example:

Oxidation reaction.

Why are decomposition reactions called the opposite of combination reactions ? Explain with equations of these reactions.

Explain the pH change as the cause of tooth decay. How can tooth decay caused by pH change be prevented?

How would you convert:

1. Ethanol into ethene?
2. Propanol into propanoic acid?

Name the process in each case and write the equations of the reactions involved.

Name the functional groups present in the following compounds:

1. CH₃CHO
   
2. CH₃CH₂COOH
   
3. CH₃COCH₃
   
4. CH₃CH₂CH₂OH
   

Grapes hanging on the plant do not ferment but after being plucked from the plant can be fermented. Under what conditions do these grapes ferment? Is it a chemical or a physical change?

Helium and neon are unreactive gases. What, if anything, do their atoms have in common?