For manufacturing of glass, which among the following is used as a source of silica?

Which one among the following is used in bleaching of paper?

Which one among the following is commonly used as an 'anti-skinning agent' in paints ?

Common salt (NaCl) is not used as a raw material for preparation of which one of the following compounds ?

Which one of the following is used in preparing a natural mosquito repellent?

Which one of the following is not a pigment?