Answer:
<u><em>(B.) a significantly lower mass that protons</em></u>
Explanation:
The mass (in g) of an electron is 9.11 ×
g, which is significantly lower than the mass of protons and neutrons which are approximately the same. They are extremely small (equal to 0 amu), contributing nothing to the overall mass of the atom.
The nucleus has a mass of 1 amu and is positively charged.
I hope you understand my working:
1) Finding the mol of NH3 to find the mol of (NH4)2SO4 (ammonium sulfate)
2) Mr of (NH4)2SO4
3) Theoretical yield: The actual grams of (NH4)2SO4 produced when reacting 0.514 mol of NH3 to 0.514 mol H2SO4
4) Using formula of (given grams)/(theoretical grams or actual grams) * 100 = 73%
5) Basic algebra