A pure titanium cube has an edge length of 2.78 in. How many titanium atoms does it contain? Titanium has a density of 4.50g/cm3

2.78 in is equivalent to 7.06 cm

volume of the cube = (7.06) ^3 = 351.9 cm^3

density can be calculated using the following rule:

density = mass / volume

therefore:

mass = density x volume

we have both the density and the volume, therefore, we can substitute to get the mass of the cube as follows:

mass of cube = 4.5 x 351.9 = 1583.5 grams

from the periodic table: mass of titanium = 47.88 grams/mole

to know the number of moles, we simply divide the mass by the molar mass.

number of moles in cube = 1583.5 / 47.88 = 33.1 moles

Each mole contains Avogadro's number of atoms, therefore:

number of atoms in 33.1 moles = 33.1 x 6.02 x 10^23 = 1.99 x 10^25 atoms