Who among the following has explained the phenomenon of photoelectric effect?

• Max Planck

• Albert Einstein

• Neils Bohr

• Ernest Rutherford

The equivalent weight of oxalic acid in C₂H₂O₄.2H₂O is

• 45

• 63

• 90

• 126

13.

On exposure to moist air, copper gains a green coat on its surface due to formation of which one of the following compounds?

• Copper carbonate

• Copper oxide

• Copper sulphate

• Copper nitrate

Which one of the following will NOT produce carbon dioxide on reacting with an aqueous solution of hydrochloric acid?

• Limestone

• Quick Lime

• Chalk

• Marble

Which one of the following substances is NOT a mixture?

• Ice

• Ice-cream

• Air

• Honey

Which one of the following is an example of Salt Crystal growth?

• Chemical weathering

• Physical weathering

• Biological weathering

• Biological weathering

Tooth enamel is made up of which one of the following calcium compounds?

• Calcium carbonate

• Calcium sulphate

• Calcium hydroxide

• Calcium phosphate

The atomic number of an element is 8. How many electrons will it gain to form a compound with sodium?

• One

• Two

• Three

• Four

A sample of oxygen contains two isotopes of oxygen with masses 16 u and 18 u respectively. The proportion of these isotopes in the sample is 3 : 1. What will be the average atomic mass of oxygen in this sample?

• 17.5 u

• 17 u

• 16 u

• 16.5 u

Which one of the following is a heterogeneous mixture?

• Hydrochloric acid

• Vinegar

• Milk

• Soda water