What is mixed with natural rubber to obtain vulcanized rubber?

State whether the following statement is true or false:
Heating ethanol at $443 \,K$ with excess concentrated sulphuric acid results in the dehydration of ethanol to give ethene.

The structural formula of ethyne is:

Which of the following are correct structural isomers of butane $(C_4H_{10})$?
$(i)$ $n$-butane: $CH_3-CH_2-CH_2-CH_3$
(ii) Isobutane ($2$-methylpropane): $CH_3-CH(CH_3)-CH_3$
(iii) Cyclobutane: $A$ four-carbon ring structure $(C_4H_8)$
(iv) Ethane dimer: Not a valid isomer of butane.

$(a)$ Differentiate between soap and detergent.
$(b)$ Explain why soaps form scum with hard water,whereas detergents do not.

The number of electron pairs shared by the two carbon atoms which are bonded by a triple bond are: