Question Video: Determining the Impurity Percentage Given the Mass of the Desired Substance and the Total Mass Chemistry

Scientists run a series of tests on an alloy and find it has a total mass of 313 g. They also determine that the alloy contains 23 g of pure gold. What is the impurity percentage of this alloy? Give your answer to two decimal places.

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Video Transcript

Scientists run a series of tests on an alloy and find it has a total mass of 313 grams. They also determine that the alloy contains 23 grams of pure gold. What is the impurity percentage of this alloy? Give your answer to two decimal places. (A) 9.27 percent, (B) 73.48 percent, (C) 7.35 percent, (D) 92.65 percent, or (E) 14.70 percent.

An alloy is a material made by combining a metallic element with one or more other elements. The alloy in the question has a total mass of 313 grams. Of this sample, 23 grams are pure gold. Using this information, we need to calculate the impurity percentage.

An impurity is an undesired material mixed in with a desired substance. In the alloy, the 23 grams of gold is the desired substance. The remaining 290 grams of the alloy is made up of impurities. We can express how impure a substance is with the impurity percentage. We can calculate a standard percentage by dividing the part in question by the whole then multiplying by 100 percent.

When calculating an impurity percentage, we want to know what part of the total sample is made up of impurities. So, to calculate an impurity percentage, we need to divide the mass of the impurities by the mass of the sample then multiply by 100 percent. We can substitute the mass of the impurities and the mass of the alloy into the equation. Performing the calculation gives us an impurity percentage of 92.6517 percent.

After rounding our answer to two decimal places, we have determined that the impurity percentage of the alloy is 92.65 percent, answer choice (D).