11). The following are the half lives of four active isotopes. Which one of the following is the most dangerous to handle?
| A). 3 billion years |
| B). 100 years |
| C). 0.01 minute |
| D). 13 days |
|
12). The method that cannot be used for removing permanent hardness of water is
| A). adding sodium carbonate |
| B). distillation |
| C). adding caustic soda |
| D). boiling |
|
13). The mineral containing both magnesium and calcium is
| A). magnesite |
| B). calcite |
| C). carnallite |
| D). dolomite |
|
14). The main chemical constituent of clay is
| A). silicon oxide |
| B). aluminium borosilicate |
| C). zeolites |
| D). aluminium silicate |
|
15). The major constituent of air is
| A). nitrogen |
| B). carbon dioxide |
| C). oxygen |
| D). hydrogen |
|
16). The ionisation energy of hydrogen atom in the ground state is x KJ. The energy required for an electron to jump from 2nd orbit to 3rd orbit is
| A). 5x/36 |
| B). 5x |
| C). 7.2 x |
| D). x/6 |
|
17). The iron ore magnetite consists of
| A). \( Fe_{2}O_{3} \) |
| B). Fe3OH4 |
| C). FeCO3 |
| D). 3Fe2O3 .. 3H2O |
|
18). The high reactivity of fluorine is due to
| A). its high electro negativity |
| B). small size of fluorine atom |
| C). availability of d-orbitals |
| D). strong F-F bond |
|
19). The inexpensive and commonly used variety of glass is called soda glass. It is called so because
| A). was used initially for making bottles of soda(carbonated drink) |
| B). is made using soda(sodium carbonate) |
| C). was initially used for storing sodium carbonate |
| D). is made using soda lime |
|
20). The mass number of a nucleus is
| A). always less than its atomic number |
| B). the sum of the number of protons and neutrons present in the nucleus |
| C). always more than the atomic weight |
| D). a fraction |
|
