![]() Thus 1 mol of sucrose has a mass of 342.297 g note that more than half of the mass (175.989 g) is oxygen, and almost half of the mass (144.132 g) is carbon. ![]() We can then use these masses to calculate the percent composition of sucrose. We can use this information to calculate the mass of each element in 1 mol of sucrose, which will give us the molar mass of sucrose. A mole of sucrose molecules therefore contains 12 mol of carbon atoms, 22 mol of hydrogen atoms, and 11 mol of oxygen atoms. First we will use the molecular formula of sucrose (C 12H 22O 11) to calculate the mass percentage of the component elements then we will show how mass percentages can be used to determine an empirical formula.Īccording to its molecular formula, each molecule of sucrose contains 12 carbon atoms, 22 hydrogen atoms, and 11 oxygen atoms. This means that 100.00 g of sucrose always contains 42.11 g of carbon, 6.48 g of hydrogen, and 51.41 g of oxygen. ![]() For example, sucrose (cane sugar) is 42.11% carbon, 6.48% hydrogen, and 51.41% oxygen by mass. With few exceptions, the percent composition of a chemical compound is constant (see law of definite proportions).-the percentage of each element present in a pure substance-is constant (although we now know there are exceptions to this law). * Note: "weight" is really entered as mass Supplemental MaterialsĬ law of definite proportions states that a chemical compound always contains the same proportion of elements by mass that is, the percent composition The percentage of each element present in a pure substance. If you had a rock that weighted 100g and contained 10g of gold, you would say that it was 10% ( w/w) ore. If you are making instant coffee, you might blend 10 g of Santa with 100 mLs of water. In that case you would have a 10% ( v/v) solution. You might mix 10 mLs of gin with 90 mLs of tonic. Solids are easier to weigh, while liquids are easier to measure volume. These different variations of % are practical to chemists and cooks. There are a number of common methods for describing percent composition of solutions, such as: weight percent, volume percent, or weight/volume percent.
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