If time required for 90 % completion of a first order reaction is '$t$'. What is the time required for 99.9 % completion of reaction at same temperature?

Identify a nanomaterial having all three dimensions less than 100 nm?

Which from following is NOT an example of oil in water emulsion?

Which from following catalysts is used in contact process of industrial production of sulfuric acid using $\text{SO}_2$ and $\text{O}_2$ (air).