I need help with these questions they are concerning density.  This is general chemistry
. If you could help me with how to do these problems.

A rectangular block of lead has a mass of 175.3 g calculate the height of the block if the width is 2.25 cm and that length is 3.15 cm

An iron ore weighing 83.245 g was placed in a flask having a volume of 54.25 ml.  The flask with the iron ore was then filled with water and weighed.  The iron ore and water weighed 124.481 g.  The density of water is 0.9976 G/ml.  Calculate the density of the iron ore.

Thank you

kingchemist Thu, 02/03/2011 - 05:13

Volume of block = L x w x h = 3.15 x 2.25 x h

If this was gold, the density = 19.3g/cm3, so 19.3g has a volume of 1 cm3.
If d = m/v, the v=m/d = 175.3/19.3 = 9.08 cm3
so if the volume = 9.08 cm3 and volume = 3.15 x 2.25 x h

then 9.08 = 3.15 x 2.25 x h

Solve for h (obviously use the density you have for lead

An iron ore weighing 83.245 g was placed in a flask having a volume of 54.25 ml.  The flask with the iron ore was then filled with water and weighed.  The iron ore and water weighed 124.481 g.  The density of water is 0.9976 G/ml.  Calculate the density of the iron ore.

If the iron ore and water weigh 124.481g and the iron ore weighs 83.245g the mass of water = 124.481-83.245g.
Take this mass of water and use the density of water to find the volume of this mass of water. (v=m/d). Then subtract this from the volume of the flask to find the volume of the iron ore