# Question Video: Calculating the Percent by Mass of the Active Ingredient in an Anti-inflammatory Ointment Chemistry

50 g of anti-inflammatory ointment was found to contain 1.1 g of the main active ingredient. What is the percent by mass of the active ingredient in this ointment?

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### Video Transcript

50 grams of anti-inflammatory ointment was found to contain 1.1 grams of the main active ingredient. What is the percent by mass of the active ingredient in this ointment?

In order to find the percent by mass of the active ingredient in this ointment, we must recognize the key equation: percent concentration by mass is equal to the mass of the solute divided by the mass of the solution times 100 percent. To use this equation, we should recognize a few key terms. The solute is the substance that is dissolved. The solvent is the substance doing the dissolving, and the solution is a mixture produced by combining the solute and solvent.

In this problem, the main active ingredient is the solute, and the anti-inflammatory ointment is the solution. We can substitute the mass of the active ingredient and the mass of the anti-inflammatory ointment into the key equation. Make sure that the mass units match before solving. We perform the calculation and determine that the percent by mass of the active ingredient in this ointment is 2.2 percent.