I need help, my answer is still incorrect after 7 try’s !

Question

A pycnometer is a glass flask with a tight fitting glass stopper that can be used to determine the density of an insoluble solid by measuring the volume of water eject it out of the pycnometer when sample of the solid is placed in it. Determine the density In g/cm^3 of an unknown metal alloy sample from the following measurements. Assume the density of water is 1.000 g/cm^3.

mass of clean pycnometer = 25.151g

mass if clean pycnometer plus water = 42.481g

mass if clean pycnometer plus metal sample = 40.505g

mass of clean pycnometer plus metal plus water = 54.265g(after ejected water is dried from the outside surface)

Answer 1

Density is mass/volume (D = M/V) and, in this case, we are trying to find the density of the unknown solid so:

Density_{(unknown solid)} = (mass_{(unknown solid)})(volume_{(unknown solid)})

The mass of the unknown solid is the mass of the clean pycnometer plus metal sample (40.505g) - mass of clean pycnometer (25.151g) = 40.505 - 25.151 = 15.354 g

Now we need to volume of the unknown solid. It happens that the volume of the unknown solid is the same as the volume of the ejected water. To find this, we need to use the equation D = M/V which we can change to V = M/D by multiplying both sides by V and then dividing both sides by D. We are given that the density of water is 1.000 g/cm³ so all we need is the mass of the ejected water.

We are given that the mass of the clean pycnometer plus water = 42.481g and we already calculated the mass of the unknown solid so the combination is 42.481 + 15.354 = 57.835 g

We are given that the mass after the water is ejected is 54.265 g so the mass of the ejected water must be 57.835 - 54.265 = 3.57g. Using V = M/D we can calculate the volume of the ejected water to be 3.57/1.000 = 3.57 cm³, which, again, is also the volume of the unknown solid.

So, the final calculation is D = mass/volume = 15.354/3.57 = 4.301 g/cm³ (we use 4 significant figures because we are given the density of water with 4 significant figures)