An atom of 125sn has a mass of 124.907785 amu. calculate the mass defect (deficit) in amu/atom. use the masses: mass of 1h atom = 1.007825 amu mass of a neutron = 1.008665 amu 1 amu = 931.5 mev give your answer to 4 significant figures and do not use e notation..

The mass defect is 1.133 amu/atom

Explanation:

The given element is:-  

Atomic number : It is defined as the number of electrons or number of protons present in a neutral atom.

Also, atomic number of Sn = 50

Thus, the number of protons = 50

Mass number is the number of the entities present in the nucleus which is the equal to the sum of the number of protons and electrons.

Mass number = Number of protons + Number of neutrons

125 =  50 + Number of neutrons

Number of neutrons = 75

Mass of neutron = 1.008665 amu

Mass of proton = 1.007825 amu

Calculated mass = Number of protons*Mass of proton + Number of neutrons*Mass of neutron

Thus,  

Calculated mass = (50*1.007825 + 75*1.008665) amu = 126.041125 amu

Given, mass = 124.907785 amu

Mass defect = Δm = |126.041125 - 124.907785 | amu = 1.13334 amu

Hence, the mass defect is 1.133 amu/atom

your answer would be a. 12.5 kg

b. accuracy of the data matters alot more than its number of digits, organization or amount of detail. quantitative observation is more accepted than the qualitative observation.