A student is trying to determine the identity of some pieces of an unknown substance by finding their density. He finds the mass of a weighing boat to
be 2.69 g and the mass of the unknown pieces, including the weighing
boat, to be 18.01 g. To find the volume of the pieces, he measured out 25.7
mL of water in a graduated cylinder and then added the pieces to find a
new volume of 32.3 ml. What is the identity of the substance?
Density
2.16
Mineral
Halite
2.32
Gypsum
Quartz
2.65
2.72
Calcite
3.18
Fluorite
O halite
O quartz
O
O gypsum
fluorite
juju

Answer : The identity of the substance is gypsum.

Explanation : Given,

Mass of weighing boat = 2.69 g

Mass of unknown pieces including weighing boat = 18.01 g

Initial volume = 25.7 mL

Final volume = 32.3 mL

First we have to calculate the mass of unknown pieces.

Mass of unknown pieces = Mass of unknown pieces including weighing boat - Mass of weighing boat

Mass of unknown pieces = 18.01 g - 2.69 g

Mass of unknown pieces = 15.32 g

Now we have to calculate the volume of unknown pieces.

Volume of unknown pieces = Final volume - Initial volume

Volume of unknown pieces = 32.3 mL - 25.7 mL

Volume of unknown pieces = 6.6 mL

Now we have to calculate the density of unknown pieces.

Now putting all the given values in this formula, we get:

From the given table we conclude that the unknown piece is gypsum whose density is 2.32 g/mL.

Therefore, the identity of the substance is gypsum.