Agraduated cylinder is filled with water to a level of 40.0 ml . when a piece of copper is lowered in to a cylinder, the water level rises to 63.4 ml. find the volume of the copper sample. if density of the copper is 8.9 g/cm^3, what is its mass?

To answer this question, you need to find the volume of the copper by dividing the final volume of the cylinder with initial volume. The calculation would be: 
63.4ml-40ml= 23.4ml

Then, to find the copper mass you need to multiply the volume with the density. Since 1ml=1cm3 you don't need to convert it. The calculation would be:
23.4ml * 1cm3/ml * 8.9g/cm^3= 208.26gram

Fine out you self hx

A)  it is neutral because the concentration of hydronium ions equals that of hydroxide ions