Percent Composition in Chemical Compounds

The video tutorial explains how to find the percent composition by mass for each element in copper(II) bromide (CuBr2). It begins by calculating the percent composition of copper, using its molar mass and the number of copper atoms in the compound. The process involves multiplying the molar mass by the number of atoms, dividing by the molar mass of CuBr2, and multiplying by 100 to get a percentage. The same method is applied to calculate the percent composition of bromine, considering there are two bromine atoms in the compound. The video concludes by verifying that the sum of the percentages is close to 100%, which confirms the accuracy of the calculations.

What is the first step in finding the percent composition by mass for an element in a compound?

• Find the atomic number of the element

• Identify the color of the compound

• Determine the number of moles of the element

• Calculate the molar mass of the compound

How do you calculate the percent composition of copper in CuBr2?

• Multiply the atomic mass of copper by the number of bromine atoms

• Divide the atomic mass of copper by the molar mass of CuBr2 and multiply by 100

• Subtract the atomic mass of bromine from the molar mass of CuBr2

• Add the atomic masses of copper and bromine

What is the percent composition by mass of copper in CuBr2?

• 63.55%

• 28.66%

• 71.33%

• 99.99%

What should you remember when calculating the percent composition for bromine in CuBr2?

• There is only one bromine atom

• The molar mass of copper is irrelevant

• There are two bromine atoms

• The atomic mass of bromine is not needed

What is the percent composition by mass of bromine in CuBr2?

• 28.66%

• 63.55%

• 71.33%

• 99.99%

What should the sum of the percent compositions of all elements in a compound be?

• 100%

• 50%

• 150%

• 75%

What is the acceptable range for the sum of percent compositions in a compound?

• 98% to 102%

• 99.99% to 100.01%

• 90% to 110%

• 95% to 105%

Who is the presenter of the video tutorial?

• Dr. A

• Dr. B

• Dr. C

• Dr. D