Question

How many formula units of CaO are in 32.7 g of CaO?

A) 0.58 formula units

B) 1.96 x 1025 formula units

C) 56.08 formula units

D) 3.51 x 1023 formula units

Answer 1

To find the number of CaO formula units in 32.7 g, we calculate the molar mass of CaO and then use Avogadro's number. The calculation leads to approximately 3.52 × 10^23 formula units, which is answer choice D.

Step-by-step explanation:

We need to calculate the number of formula units of CaO in 32.7 g of CaO. First, we find the molar mass of CaO by adding the atomic mass of calcium (Ca, 40.08 g/mol) and the atomic mass of oxygen (O, 16.00 g/mol). The molar mass of CaO is therefore 40.08 g/mol + 16.00 g/mol = 56.08 g/mol.

Next, we use the formula:

Number of formula units = (mass in grams / molar mass) × Avogadro's number

Using the mass of CaO we have (32.7 g / 56.08 g/mol) × 6.022 × 10^23 formula units/mol. This gives us 3.52 × 10^23 formula units (rounded to three significant figures) of CaO, which matches choice D.

Answer 2

D) 3.51x10²³ formula units

Step-by-step explanation:

To know this, we need to calculate the molecular mass of CaO. To do that, let's use the atomic mass of each element of this compound.

Ca: 40.08 g/mol; O: 16 g/mol

With these given AM, let's calculate the molar mass of CaO:

Mm CaO = 40.08 + 16 = 56.08 g/mol

Now that we have the MM of CaO, it's time to determine the moles of CaO:

moles = mass / MM

moles = 32.7 / 56.08 = 0.5831 moles

Finally to get the formula units, we need to use the Avogadro's number which is 6.02x10²³. According to this number, 1 mole of any substance has this number of atoms, molecules or formula units. So, if we have 0.5831 moles, then the formula units will be:

FU = 0.5831 * 6.02x10²³

FU = 3.51x10²³ formula units

Hope this helps