Question

A 5.5 g sample of a substance contains only carbon and oxygen. Carbon makes up 35% of the mass of the substance. The rest is made of oxygen. You are asked to determine the mass of oxygen in the sample. Which of the following expressions demonstrates a mathematical procedure to solve this problem using the proper order of operations? 1) ((100 - 35)/100) times 5.5 grams = 2)100 - 35/100 times 5.5 grams = 3) 100 - (35/100) times 5.5 grams = *Recall that to calculate a percent of an amount in grams means you have to convert the percent to a number and multiply by the amount in grams. For example, 50% means 50 out of 100, or 50 hundredths. So 50% of 10 grams is 0.50 times 10 grams. You need to take 0.50 and multiply it by 10 grams to determine 50% of 10 grams is 5.0. (50% and 10 grams are examples and not numbers for this problem.)

Answer 1

Answer:

The correct answer is option (1).

Explanation:

Mass of the sample = 5.5 g

Percentage of carbon in sample = 35 %

Percentage of oxygen in sample = 100% - 35%

$\%=\frac{\text{Mass of the element in the sample}}{\text{Mass of sample}}\times 100$

Mass of carbon in a sample: (35%) of 5.5 g

$\frac{35}{100}\times 5.5 g=1.925 g$

Mass of oxygen in a sample: (100%-35%) of 5.5 g

$\frac{100-35}{100}\times 5.5 g=3.575 g$