Answer:
1.878g
Explanation:
Volume = 30.0ml
Density = 0.626gcm−3
Mass = ?
Be careful in this kind of questions to check for the units. In this case one has to remember 1 mL equal 1 cm³ so density = 0.626g/ml
The relationship between all three parameters is given by the equationn below;
Mass = Density * Volume
Mass = 0.626g/ml * 30 = 1.878g
Explanation:
High density medium to low density medium.
Density is mass divided by volume. Therefore, volume is mass divided by density.

Percent composition by mass of oxygen =
((16.0*6)/(40.1+2*(14.0+16.0*3)))*100%
= 58.5%
therefore, the answer is D
C. The number of protons in the atoms nucleus.