Percent Compositions of Compound| Grade 9 Science Quarter 2 Week 8 | DepEd MELC-based

good day students welcome back to my estranged youtube channel we are down with our last lesson for quarter two week eight topic is about percent composition of compounds if you haven't watched our week 1 to 6 lessons check our description box for the links for today's learning objective you will be able to determine the percentage composition of a compound given its chemical formula and vice versa so what are you waiting for keep on watching [Music] suppose that you had your second periodical examination in science when you get a score of 85 percent in the exam it means that you have answered 85 correctly or you answered 85 items correctly another example to understand more is an instant coffee are you one of those coffee is life person let's say for example the three-in-one or instant coffee is consist of coffee sugar and milk one sachet of an instant coffee has 10 grams of coffee 13 grams of sugar 12 grams of milk the sum of these three ingredients will be 35 grams of three-in-one coffee now let us calculate the percent composition of coffee sugar and milk in a three-in-one coffee sachet 10 grams of coffee divided by 35 grams equals 0.285714 and so on times 100 per result is 28.5714 and so on do not forget to round off to the nearest hundredths and our final answer will be 28.57 now let us proceed to the 13 grams of sugar divided by 35 grams times 100 percent and again let us round off to the nearest hundredths the final answer is 37.14 lastly we have 12 grams of milk divided by 35 grams times 100 and then round off to the nearest hundredths the final answer will be 34.29 summing up these products the result is 100 in the laboratory you may perform experiments that will require you to prepare solutions or to verify the purity of some substances thus you need to know how to calculate the percent compositions of compounds and this is our formula mass percent is equal to mass of element divided by mass of compound multiplied to 100 percent let's have an example ethanol an alcohol obtained by fermenting the sugar in grapes corn and other fruits and grains with the chemical formula of c2h6o is often added to gasoline as an octane enhancer to form a fuel well called gasol let us calculate the mass percent of ethanol take note class that one mole of ethanol molecules consists of two moles of carbon atoms six moles of hydrogen atoms and one mole of oxygen atom now let us calculate the percent compositions of ethanol first let us determine the molar mass from its chemical formula we know that we have two carbon atoms six hydrogen atoms and one oxygen atom by looking at the periodic table of elements we can determine that the atomic mass of carbon is 12.01 gram per mole times two because we have two carbon atoms the product is 24.02 gram per mole the atomic mass of hydrogen by looking at the periodic table of elements is 1.008 gram per mole multiplied to 6 because we have 6 hydrogen the result is 6.048 gram per mole lastly the atomic mass of oxygen is 16.0 gram per mole multiplied to 1 the product is 16.0 gram per mole to get the molar mass let us add their products and that is 46.068 gram per mole do not forget to round off our final answer to the nearest hundredths therefore the molar mass of ethanol or c2h6o will be 46.07 gram per mole now let us calculate the mass percent let us start with mass percent of carbon using our formula mass percent of carbon in one mole of ethanol divided by mass of one mole of ethanol times 100 and that is 24.02 grams divided by 46.07 grams the quotient is 0.521380 and so on times 100 do not forget class to round off to the nearest hundredths the product and the final answer will be 52.14 now let us proceed to the mass percent of hydrogen the mass percent of hydrogen and oxygen in ethanol are obtained in a similar manner we have 6.048 grams divided by 46.07 grams times 100 percent final answer is 13.14 remember round off to the nearest hundredths lastly we have the mass percent of oxygen same process just like what we did with carbon and hydrogen the mass of oxygen is 16.0 gram and the mass of ethanol is 46.07 gram this is the quotient times 100 and round off to the nearest hundredths the final answer is 34.73 percent reminder class the mass percent of all the elements in a compound add up to 100 although rounding off effects may produce small deviation adding up the percentages is a good way to check your final answer or to check your calculations let us try to visualize ethanol using a pie chart [Music] now let us summarize our lesson for today percent composition is used to find the percentage of elements in a compound you must know the molar mass of the elements and the compound in order to get percent composition in chemistry percent composition is important to analyze and to determine the empirical formula of a chemical substance and that is it for our lesson this week do not forget to finish all your learning tasks and also don't be shy to comment down your questions and if this video helped you do not forget to click the like share and subscribe button to keep you updated for future videos turn on the bell button thank you so much for watching see you on my next one bye

Channel: Maestrang Techy

Views: 62,098

Keywords: Percentage Composition, Mass Percent of a Compound, Percentage of a Compound, Mass percent, Chemistry lesson, Percentage, Grade 9, Deped, Melc-based lesson, calculate the percent mass, Grade 9 Science

Id: DokPXwKAEAk

Length: 9min 1sec (541 seconds)

Published: Mon Feb 22 2021