Q.21)-The mass number of a nucleus is
- always less than its atomic number
- the sum of the number of protons and neutrons present in the nucleus
- always more than the atomic weight
- a fraction
Q.22)-The hydronium ion is
- H+
- HO -
- H2+
- H3O+
Q.23)-The most electropositive elements among the following is
- Na
- Ca
- K
- Cs
Q.24)-The method that cannot be used for removing permanent hardness of water is
- adding sodium carbonate
- distillation
- adding caustic soda
- boiling
Q.25)-Zone refining is used for the purification of
- Au
- Ge
- Ag
- Cu
Q.26)-The high reactivity of fluorine is due to
- its high electro negativity
- small size of fluorine atom
- availability of d-orbitals
- strong F - F bond
Q.27)-The major constituent of air is
- nitrogen
- carbon dioxide
- oxygen
- hydrogen
Q.28)-The main chemical constituent of clay is
- silicon oxide
- aluminium borosilicate
- zeolites
- aluminium silicate
Q.29)-The mineral containing both magnesium and calcium is
- magnesite
- calcite
- carnallite
- dolomite
Q.30)-The main active constituent of tea and coffee is
- nicotine
- chlorophyll
- caffeine
- aspirin