Q&A for How to Calculate Mass Percent

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  • Question
    If a solution is prepared by mixing 50 ml of vinegar into 300 ml of solution, what is the percentage by volume?
    Bess Ruff, MA
    Environmental Scientist
    Bess Ruff is a Geography PhD student at Florida State University. She received her MA in Environmental Science and Management from the University of California, Santa Barbara in 2016. She has conducted survey work for marine spatial planning projects in the Caribbean and provided research support as a graduate fellow for the Sustainable Fisheries Group.
    Environmental Scientist
    Expert Answer
    You can use the same formula to calculate percentage by volume as you use to calculate percentage by mass. First, calculate the total volume of the solution. Then, divide the volume of the vinegar by the total volume of the solution. Finally, multiply by 100 to get the percentage of vinegar in the total solution. 50 ml + 300 ml = 350 ml for the total volume of the solution. Vinegar percentage = 50/350 = 14 x 100 = 14% vinegar.
  • Question
    How do I determine the mass percentage of salt (NaCl) in a water-salt solution?
    Community Answer
    In order to calculate the mass percentage, you must know how much salt was added to a certain amount of water. For instance, if you added 50 grams of NaCl to 1000 grams of water, that mass percent would be 50/1050 x 100 = 4.76%.
  • Question
    How would I calculate the mass percent of a MgBr2 solution that contains 5.80g of MgBr2 in 45.0g of solution?
    Community Answer
    Similar to the example given above, simply plug the numbers into the mass percent equation. Calculate total mass of the compound: 5.8 + 45 = 50.8. Divide mass of the chemical by mass of the compound and multiply by 100: 5.8/50.8 x 100 = 11.42%.
  • Question
    How do I find the mass percent of a compound of a mixture?
    Community Answer
    You divide the mass of the element or compound you are looking for by the total mass of the compound. Don't forget to have the same units of mass for both numbers.
  • Question
    How do I calculate mass percentages?
    Community Answer
    Follow the instructions listed in the article above.
  • Question
    A solution of urea in water contains 18 grams of urea in 200 grams of solution. How do I find out the mass percentage?
    Community Answer
    (18 grams) / (200 grams + 18 grams), then multiplied by 100, which equals 8.3% (rounded up).
  • Question
    What is the formula of percent by mass?
    Community Answer
    The basic formula for mass percent of a compound is: mass percent = mass of chemical/total mass of compound x 100. (You must multiply by 100 at the end to express the value as a percentage.)
  • Question
    How do I calculate the mass percent of the different elements present in sodium sulfate Na2So4?
    Community Answer
    The molecular formula of sodium sulphate is (Na2SO4). Molar mass = atomic mass of Na (23) + atomic mass of S (32.066) + atomic mass of O (16). Molar mass of (Na2SO4) = [(2 × 23.0) + (32.066) + 4 (16.00)] = 142.066.
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