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).
