We can calculate the mass percent of an element by dividing its atomic mass by the mass of the compound and then multiply by 100:
% by mass of element = (mass of element/mass of compound) x100%
Impurities like n-eicosane with the molecular formula C20H42 could account for the low percent by mass of oxygen in the sample because it has a zero percent oxygen based on its compound formula which indicates that it does not have the element oxygen.
Answer:

Explanation:
Mol of NaI = 0.405 mol
Molarity of solution = 0.724 M
Molarity is given by

The required volume is
.
Answer:
A.0.20M
Explanation:
c 1 V 1 = c 2 V 2
Initial Volume, V1 = 200 mL
Final Volume, V2 = 200 + 400 = 600 mL
Initial Concentration, c1 = 0.60 M
Final Concentration, c2= ?
Solving for c2;
c2 = c1v1 / v2
c2 = 0.60 * 200 / 600
c2 = 0.20M
Boiling and melting points are physical properties because they do not change the chemical nature of the substance whose properties you are measuring.
Flat as more oxygen and water can react over it think of it like this would a cube rust faster than a sheet