Calculating Molecular Weights and Formulas

The video tutorial explains how to calculate the molecular weight or molar mass of lead(II) nitrate, Pb(NO3)2. It begins by identifying the atomic weights of lead, nitrogen, and oxygen from the periodic table. The tutorial then demonstrates how to apply the subscripts in the chemical formula to calculate the total molar mass, emphasizing the importance of correctly using parentheses and brackets to account for multiple atoms. The final calculation is presented, and the video concludes with a summary of the process.

What is the atomic weight of lead (Pb) as mentioned in the video?

• 207.2 g/mol

• 27.2 g/mol

• 14.0 g/mol

• 16.0 g/mol

How is the atomic weight of nitrogen (N) rounded for calculation?

• 14.01

• 14.0

• 15.0

• 16.0

What is the rounded atomic weight of oxygen (O) used in the calculation?

• 17.0

• 14.0

• 16.0

• 15.999

In the formula Pb(NO3)2, to which element does the subscript '3' apply?

• Oxygen (O)

• Nitrogen (N)

• Lead (Pb)

• The entire nitrate group

What is the purpose of the brackets in the formula Pb(NO3)2?

• To separate lead from nitrate

• To apply the subscript 2 to the entire nitrate group

• To denote a chemical reaction

• To indicate multiplication by 3

What is the result of multiplying 16.0 by 3 in the calculation?

• 33.2 g/mol

• 48.0 g/mol

• 62.0 g/mol

• 207.2 g/mol

What is the final molecular weight of lead(II) nitrate (Pb(NO3)2) as calculated in the video?

• 207.2 g/mol

• 33.2 g/mol

• 331.2 g/mol

• 62.0 g/mol

What is the first step in calculating the molecular weight of a compound?

• Look up atomic weights on the periodic table

• Multiply all subscripts

• Add all atomic weights

• Divide by the number of atoms

What should you do when dealing with multiple subscripts in a chemical formula?

• Break it up and do the math inside first

• Multiply them directly

• Ignore them

• Add them together