Which of the following is the use of propanone?

Alkynes may be represented by the general formula:

State whether the following statement is true or false:
Scum is formed due to the reaction of soap with calcium and magnesium salts present in hard water.

Explain why washing clothes with hard water is not effective.

Carbon exists in the atmosphere in the form of

Draw the electron-dot structure for ethyne. $A$ mixture of ethyne and oxygen is burnt for welding. In your opinion,why cannot we use a mixture of ethyne and air for this purpose?