Textbook Question
A sample of the male sex hormone testosterone, C19H28O2, contains 3.88×1021 hydrogen atoms. (c) How many moles of testosterone does it contain? (d) What is the mass of this sample in grams?
Ch.3 - Chemical Reactions and Reaction Stoichiometry
Chapter 3, Problem 44a
At least 25 mg of tetrahydrocannabinol (THC), the active ingredient in marijuana, is required to produce intoxication. The molecular formula of THC is C21H30O2. How many moles of THC does this 25 mg represent?
Verified step by step guidance1
First, convert the mass of THC from milligrams to grams. Since there are 1000 milligrams in a gram, divide 25 mg by 1000 to get the mass in grams.
Next, calculate the molar mass of THC using its molecular formula, C21H30O2. Add up the atomic masses of all the atoms in the formula: 21 carbon atoms, 30 hydrogen atoms, and 2 oxygen atoms.
The atomic masses are approximately: Carbon (C) = 12.01 g/mol, Hydrogen (H) = 1.01 g/mol, and Oxygen (O) = 16.00 g/mol. Multiply each atomic mass by the number of atoms of that element in the formula and sum them to find the molar mass of THC.
Now, use the formula for moles: moles = mass (g) / molar mass (g/mol). Substitute the mass of THC in grams and the molar mass you calculated into this formula.
Finally, solve the equation to find the number of moles of THC that 25 mg represents.
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Molecular Formula
The molecular formula of a compound indicates the number of each type of atom present in a molecule. For THC, C21H30O2 means it contains 21 carbon atoms, 30 hydrogen atoms, and 2 oxygen atoms. Understanding the molecular formula is essential for calculating the molar mass, which is necessary for converting mass to moles.
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Determining Molecular Formulas
Molar Mass
Molar mass is the mass of one mole of a substance, typically expressed in grams per mole (g/mol). To find the molar mass of THC, you sum the atomic masses of all atoms in its molecular formula. This value allows you to convert between grams and moles, which is crucial for determining how many moles correspond to a given mass of the substance.
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Mole Concept
The mole is a fundamental unit in chemistry that quantifies the amount of substance. One mole contains approximately 6.022 x 10^23 entities (Avogadro's number), whether they are atoms, molecules, or ions. Understanding the mole concept is vital for performing stoichiometric calculations, such as converting the mass of THC into moles to assess its effects.
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Related Practice
Textbook Question
The allowable concentration level of vinyl chloride, C2H3Cl, in the atmosphere in a chemical plant is 2.0×10−6 g/L. How many moles of vinyl chloride in each liter does this represent?
Textbook Question
The allowable concentration level of vinyl chloride, C2H3Cl, in the atmosphere in a chemical plant is 2.0⨉10−6 g/L. How many molecules per liter?
Textbook Question
At least 25 mg of tetrahydrocannabinol (THC), the active ingredient in marijuana, is required to produce intoxication. The molecular formula of THC is C21H30O2. How many molecules?
Textbook Question
Give the empirical formula of each of the following compounds if a sample contains (a) 0.052 mol C, 0.103 mol H, and 0.017 mol O
Textbook Question
Give the empirical formula of each of the following compounds if a sample contains (b) 2.10 g nickel and 0.58 g oxygen
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