When atoms are considered most of the mass lies in the nucleus which has neutrons and protons. Hence the statement is true because on comparing weight of neutron and proton to the mass of electron, mass of electron will be negligible.
The mass {atomic} of any material is actually the mass we get on adding masses of proton and neutron. Electrons are about 104 kg are lighter than the mass of proton Neutron in the mass of proton and neutron and nearly equal to each other.
12. B
13. B
14.D
15. A.
16.C.
17. C
18.B
19.A.
Explanation:
Water can be purified from through...
Filtration - This involves the use of filter paper to remove solid objects found in water.
Boiling - This involves keeping water at 100 deg celcius for a while through application of heat and this kills microorganisms in the water.
Addition of alum - Alum causes very fine and small particles that are suspending in water to stick together making them large enough to be removed through filtration.
Chemicals used in water treatment...
Chlorine - Chlorine is used to kill bacteria, viruses and other disease causing pathogens found in water
That's all I know...
1.)<span>1.5 atm= 1140mm Hg
2.)190mm Hg= .25 atm
3.)253mm Hg= 0.332895 atm
4.).2 atm =152mm Hg
5.)1.5mm Hg= 0.199984 kPa
6.)190mm Hg= 25.3313 kPa
7.)103.2 kPa= 774.06355mm Hg
8.)153mm Hg= 20.3983 kPa
9.)99.8 kPa= </span>0.9849494 atm
Optrion A: when trying to determine a star's chemical composition.
Because unique atomic emission spectrum, analyzing the emission spectrum you can tell the chemical composition.