Which acid is found in vinegar?

Percentage of lead in lead pencil is: 

Which of the following is the lightest element in the universe? 

In which of the following chlorine has + 1 oxidation number?

Burning of Hydrogen produces 

Which of the following metals can be cut with a knife?

Thin wires can be pulled from a metal piece. For which property of the metal is it responsible?

The atoms, in which the number of Protons is same but the number of neutrons is different, are known as –