Yes, a solid has a fixed volume.
Answer:

Explanation:
Hello,
In this case, assuming oxygen as an ideal gas, it is described by:

Whereas the gas constant R is required, therefore, it is computed as shown below:

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The reaction is given as
Fe2O3 (s)+ 3CO(g)--->3CO2(g)+ 2Fe(s)
No.of moles=mass in gram/molar mass
As for Fe mole =156.2g/55.847=2.7969~2.797
The ratio b/w CO and Fe is 3:2
Moles of CO needed= 2.797x3/2=4.1955
Mass of CO needed= 4.195mol x 28.01g/mol= 117.515g
The buoyancy of an object is dictated by its density. So let us calculate for density, where:density = mass / volume
Calculate the volume first of a solid cube:volume = (6 cm)^3 = 216 cm^3 = 216 mL
Therefore density is:density = 270 g / 216 mLdensity = 1.25 g / mL
Therefore this object will float in the layer in which the density is more than 1.25 g / mL.