Textbook Question
Determine the formula weights of each of the following compounds: e. benzaldehyde, C6H5CHO, the molecule largely responsible for the odor of almond extract.
Ch.3 - Chemical Reactions and Reaction Stoichiometry
Chapter 3, Problem 25b
Calculate the percentage by mass of oxygen in the following compounds: b. codeine, C18H21NO3
Verified step by step guidance1
Step 1: First, we need to calculate the molar mass of codeine. The molar mass of a compound is calculated by adding up the molar masses of each element in the compound. The molar mass of carbon (C) is approximately 12.01 g/mol, hydrogen (H) is approximately 1.01 g/mol, nitrogen (N) is approximately 14.01 g/mol, and oxygen (O) is approximately 16.00 g/mol. So, the molar mass of codeine, C18H21NO3, is (18*12.01 g/mol) + (21*1.01 g/mol) + (14.01 g/mol) + (3*16.00 g/mol).
Step 2: Next, we need to calculate the total mass of oxygen in the compound. This is done by multiplying the number of oxygen atoms in the compound by the molar mass of oxygen. So, the total mass of oxygen in codeine is (3*16.00 g/mol).
Step 3: Now, we can calculate the percentage by mass of oxygen in codeine. This is done by dividing the total mass of oxygen by the molar mass of codeine and then multiplying by 100 to get a percentage. So, the percentage by mass of oxygen in codeine is ((3*16.00 g/mol) / molar mass of codeine) * 100.
Step 4: Make sure to check your work. The percentage by mass of oxygen should be a reasonable number between 0 and 100. If it's not, you may have made a mistake in your calculations.
Step 5: Finally, report your answer with the correct number of significant figures. The number of significant figures in your answer should be the same as the number of significant figures in the given data.
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Molar Mass Calculation
Molar mass is the mass of one mole of a substance, typically expressed in grams per mole (g/mol). To calculate the molar mass of a compound, sum the molar masses of all the atoms in its chemical formula. For codeine (C18H21NO3), this involves calculating the contributions from carbon, hydrogen, nitrogen, and oxygen atoms based on their respective atomic weights.
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Percentage by Mass
Percentage by mass is a way to express the concentration of a particular element in a compound. It is calculated by dividing the mass of the element in one mole of the compound by the total molar mass of the compound, then multiplying by 100. This provides a clear understanding of how much of the compound's mass is due to a specific element, such as oxygen in codeine.
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Chemical Composition
Chemical composition refers to the types and amounts of elements that make up a compound. Understanding the chemical formula of a compound, like codeine (C18H21NO3), allows for the identification of the number of each type of atom present. This is essential for calculating both the molar mass and the percentage by mass of specific elements, such as oxygen.
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