Option “4” is correct. Nitrochloroform is used as anaesthetics before the operation of the patient to make them unconscious. Other options are explosive.
403. The Nucleus of Helium has-
1. Only one neutron
2. Two protons
3. Two protons and two neutrons
4. One proton and two neutrons
Option “3” is correct. Helium- (2He4) is a non-radioactive isotope of the element Helium. Its nucleus is identical to an alpha particle and consists of two protons and two neutrons.
Option “4” is correct. Solid camphor directly changes into camphor vapour and this process is called sublimation. The sublimation is the process in which some substances upon heating directly changes into vapour from and when cooled again directly turns into solid form.
406. Which one of the following is liquid at ordinary temperature?
1. Lead
2. Nickel
3. Mercury
4. Tin
Option “3” is correct. Mercury is the only common metal which is liquid at ordinary temperature.
407. Percentage of Silver in German Silver is:
1. 1%
2. 5%
3. 0%
4. None of these
Option “3” is correct. German Silver or Nickel silver is an alloy consisting 50% Copper, 35% Zinc and 15% Nickel. It doesn’t have silver.
408. In atom, neutron was discovered by:
1. J.J. Thomson
2. Chadwick
3. Rutherford
4. Newton
Option “2” is correct. Neutron is a neutral particle which has no electrical charge. It was discovered by Chadwick in 1932.
409. Change of water into the vapour is called-
1. Natural
2. Physical
3. Chemical
4. Biological
Option “2” is correct. Change of water into the vapour is called a physical change.
410. Which one of the following is the hardest metal?
1. Gold
2. Iron
3. Platinum
4. Silver
Option “3” is correct. Among non-metals, diamond is the hardest whereas, among the metals, platinum is the hardest.
