Final answer:
To find out how many molecules there are in 81.01 g of CCl4, the amount of substance is first converted from grams to moles using the molar mass of CCl4, and then the result is multiplied by Avogadro's number to get approximately 3.149 × 10²³ molecules.
Step-by-step explanation:
Calculating the Number of Molecules in CCl4
To find out how many molecules are in 81.01 g of CCl4, we need to apply stoichiometry and use the concept of molar mass and Avogadro's number. The molar mass of CCl4 is not directly provided, but it can be calculated based on the atomic weights of carbon (C) and chlorine (Cl). Since the molar mass of Cl2 is given as 70.90 g/mol, we can deduce that the molar mass of a single Cl atom is 70.90 g/mol divided by 2, which is 35.45 g/mol. Carbon has an atomic mass of approximately 12.01 g/mol. Putting this together, CCl4 has a molar mass of (1 x 12.01 g/mol) + (4 x 35.45 g/mol) = 154.81 g/mol.
To compute the number of moles of CCl4, we use the ratio:
81.01 g CCl4 x (1 mol CCl4 / 154.81 g CCl4) = 0.5231 mol CCl4
Now we use Avogadro's number, which states that 1 mole of any chemical substance contains 6.022 × 10²³ molecules. To find the number of molecules:
0.5231 mol CCl4 x (6.022 × 10²³ molecules/mol) = 3.149 × 10²³ molecules of CCl4
Therefore, there are approximately 3.149 × 10²³ molecules of CCl4 in 81.01 g of CCl4, expressed to four significant figures.