Which one of the following is not a pigment?
- (a)Zinc oxide
- (b)Chalk
- (c)White lead
- (d)Silica
Correct — D, Silica. Zinc oxide (zinc white), chalk (whiting) and white lead are all white pigments used to give paint its colour and hiding power. Silica (SiO₂) is transparent and is used as a filler, extender and abrasive, not to impart colour — so it is the one that is not a pigment.
- (a)Zinc oxide — Zinc oxide is 'zinc white', a well-known white pigment used in paints, so it is a pigment.
- (b)Chalk — Chalk (calcium carbonate, 'whiting') is used as a white pigment and extender in whitewash and paints, so it counts as a pigment.
- (c)White lead — White lead (basic lead carbonate) is a classic white pigment (now restricted for its toxicity), so it is a pigment.
A pigment is a finely divided, insoluble solid — usually white or coloured — that gives paint its colour and opacity (hiding power). Fillers or extenders, by contrast, add bulk and body but do not colour the paint; silica is a transparent extender and abrasive, not a colouring pigment.
Three of the four are recognised white pigments; silica looks like a similar fine white powder but is transparent and used to bulk out or matte a paint rather than to colour it, which is why it is the odd one out.
- Zinc white is zinc oxide (ZnO); white lead is basic lead carbonate; whiting is chalk (CaCO₃).
- Silica (SiO₂) is used as a filler, extender and mild abrasive, not as a pigment.
- Pigments are insoluble and impart colour and opacity to paint.
- White lead is toxic and its use has been heavily restricted.
- Assuming any fine white powder is a pigment — silica is a transparent extender.
- Overlooking that chalk (whiting) does serve as a white pigment, not just a filler.
Identify the odd one out — the substance that acts as a filler, not a colouring pigment.
No directly related past PYQ was found.
- practice — not a real PYQ
Titanium dioxide is used in paints mainly as a
- (a)solvent
- (b)white pigment
- (c)drying agent
- (d)thinner
Answer(b) white pigment — TiO₂ gives paint its whiteness and opacity.
- practice — not a real PYQ
Which one of the following is used as a filler or extender rather than as a pigment?
- (a)Zinc oxide
- (b)White lead
- (c)Silica
- (d)Chrome yellow
Answer(c) Silica — a transparent extender/abrasive, not a colouring pigment.