I won't give the answer, but here's the process: You have the weight of the object (0.500 lbs), and you want to convert that into the number of kernels. You are given the fact that 1 pound = 16 oz, and 1 oz=28.3 grams. So it should be apparent that you need to convert pounds to ounces first and then convert ounces to grams. Now that you the grams, you can easily figure out how many kernels there are because .125 grams equals the weight of one kernel.
Source: IGN
Atomic mass is just protons plus neutrons
Mass of Na2SO4= 514.18 grams
<h3>Further explanation</h3>
Given
423.67 g of NaCl
Required
mass of Na2SO4
Solution
Reaction
2NaCl + H2SO4 → Na2SO4 + 2HCl
mol NaCl :
= 423.67 g : 58.5 g/mol
= 7.24
From the equation, mol Na2SO4 :
= 1/2 x mol NaCl
= 1/2 x 7.24
= 3.62
Mass Na2SO4 :
= 3.62 mol x 142,04 g/mol
= 514.18 grams
Atoms or molecule after gaining of electron possesses negative charge and is known as anion.
For the given sets:
The given elements are alkali metals and have tendency to lose electrons easily and form cations.
The given elements are non-metals and are electronegative. So, they gain electrons easily and form anion.
Carbon has tendency to form bond by sharing of electrons, Sulfur has tendency to gain electrons and form anion whereas Lead has tendency to lose electron.
Potassium and Iron has tendency to lose electron and form cation whereas Bromine has tendency to gain electron to form anion.
Hence, from the given sets, all elements of set: 
have tendency to form anions in binary ionic compounds.
