Problem 78
Question
The hallucinogenic drug LSD has the molecular formula \(\mathrm{C}_{20} \mathrm{H}_{25} \mathrm{~N}_{3} \mathrm{O} .\) One suspected sample contained \(74.07 \% \mathrm{C},\) \(7.95 \% \mathrm{H},\) and \(9.99 \% \mathrm{~N}\) (a) What is the percentage of \(\mathrm{O}\) in the sample? (b) Are these data consistent for \(L S D ?\)
Step-by-Step Solution
Verified Answer
The percentage of \text{O} in the sample is 8.99\text{%}. The data are consistent for LSD because the percentages of C, H, N, and O closely match the expected percentages derived from the molecular formula of LSD.
1Step 1: Calculate the percentage of oxygen
To find the percentage of oxygen in the sample, add the given percentages of carbon, hydrogen, and nitrogen, and subtract this sum from 100%.
2Step 2: Compare the theoretical and experimental percentages
Check the consistency of the data by comparing the calculated percentage of oxygen with the theoretical percentage of oxygen in the molecular formula of LSD.
3Step 3: Analysis of the results
Determine if the calculated percentages of the elements in the sample match closely enough with the percentages that would be expected from the molecular formula of LSD.
Key Concepts
Molecular FormulaPercent Composition by MassHallucinogenic Drugs ChemistryStoichiometry
Molecular Formula
Understanding the molecular formula of a substance is crucial for analyzing its chemical composition. A molecular formula indicates the type and number of atoms in a single molecule of a compound. For example, the molecular formula for LSD is \(\mathrm{C}_{20}\mathrm{H}_{25} \mathrm{N}_{3} \mathrm{O}\). Each letter represents a different element from the periodic table: carbon (C), hydrogen (H), nitrogen (N), and oxygen (O). The numbers, called subscripts, show how many atoms of each element are present in a molecule of the compound.
For educational purposes, let's simplify: visualize the molecular formula as the 'recipe' for a molecule. Just as a recipe dictates the exact amount of each ingredient needed to bake a cake, the molecular formula tells us how many atoms of each element are needed to form a molecule of a specific compound. By knowing the formula, scientists and students can delve deeper into the compound's properties and reactions.
For educational purposes, let's simplify: visualize the molecular formula as the 'recipe' for a molecule. Just as a recipe dictates the exact amount of each ingredient needed to bake a cake, the molecular formula tells us how many atoms of each element are needed to form a molecule of a specific compound. By knowing the formula, scientists and students can delve deeper into the compound's properties and reactions.
Percent Composition by Mass
Percent composition by mass refers to the percentage ratio of each element's mass to the total mass of the compound. To calculate this for a particular element, use the formula: \[ \text{Percent Composition} = \frac{\text{Mass of element in one mole of the compound}}{\text{Mass of one mole of the compound}} \times 100\% \]
As an illustration, consider a cake you're making, where you're interested in knowing what percentage of the cake's weight comes from sugar. If you have the weight of sugar used and the total cake weight, you could find the sugar's percent composition. Similarly, chemists calculate the mass percentages of elements in compounds to understand their makeup and to help identify substances based on experimental data, which links directly to stoichiometry and the chemical's identity. This concept is foundational in exercises such as the one analyzing LSD's composition.
As an illustration, consider a cake you're making, where you're interested in knowing what percentage of the cake's weight comes from sugar. If you have the weight of sugar used and the total cake weight, you could find the sugar's percent composition. Similarly, chemists calculate the mass percentages of elements in compounds to understand their makeup and to help identify substances based on experimental data, which links directly to stoichiometry and the chemical's identity. This concept is foundational in exercises such as the one analyzing LSD's composition.
Hallucinogenic Drugs Chemistry
Hallucinogenic drugs like LSD work by affecting the neurotransmitter systems in the brain, leading to profound changes in perception, mood, and thought. The chemistry behind these drugs is fascinating and complex, involving interaction with specific receptors in the brain. The molecular structure, which can be represented by the molecular formula, plays a significant role in the drug's effects and potency.
To further simplify, think of a lock and key, where the hallucinogenic drug is the key, and the receptor in your brain is the lock. The molecular formula tells us the shape of the key, which needs to precisely fit the lock to unleash the drug's effects. This is why understanding the molecular formula and the correct composition of a hallucinogenic drug is not only crucial for pharmacology but also for ensuring safe and controlled use.
To further simplify, think of a lock and key, where the hallucinogenic drug is the key, and the receptor in your brain is the lock. The molecular formula tells us the shape of the key, which needs to precisely fit the lock to unleash the drug's effects. This is why understanding the molecular formula and the correct composition of a hallucinogenic drug is not only crucial for pharmacology but also for ensuring safe and controlled use.
Stoichiometry
Stoichiometry is essentially the math behind chemistry, dealing with the quantitative relationships that govern the mixing of elements and compounds in chemical reactions. It uses the mole concept, molar masses, and balanced chemical equations to calculate the amounts of reactants and products involved in a chemical reaction.
Imagine you're a chef trying to scale a recipe, you'll need to know precisely how much of each ingredient to use to keep the flavors balanced. In a similar sense, stoichiometry helps chemists balance chemical recipes, ensuring that atoms are neither wasted nor left over. A good understanding of stoichiometry is necessary when comparing theoretical data and experimental data, like analyzing whether the suspected LSD sample's composition matches its known molecular formula.
Imagine you're a chef trying to scale a recipe, you'll need to know precisely how much of each ingredient to use to keep the flavors balanced. In a similar sense, stoichiometry helps chemists balance chemical recipes, ensuring that atoms are neither wasted nor left over. A good understanding of stoichiometry is necessary when comparing theoretical data and experimental data, like analyzing whether the suspected LSD sample's composition matches its known molecular formula.
Other exercises in this chapter
Problem 76
An analysis revealed that \(5.67 \mathrm{~g}\) of a compound of nitrogen and oxygen contained \(1.47 \mathrm{~g}\) of nitrogen. What are the percentages by mass
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Phencyclidine ("angel dust") is \(\mathrm{C}_{17} \mathrm{H}_{25} \mathrm{~N}\). A sample suspected of being this illicit drug was found to have a percentage co
View solution Problem 79
How many grams of \(\mathrm{O}\) are combined with \(7.14 \times 10^{21}\) atoms of \(\mathrm{N}\) in the compound dinitrogen pentoxide?
View solution Problem 80
How many grams of \(\mathrm{C}\) are combined with \(4.25 \times 10^{23}\) atoms of \(\mathrm{H}\) in the compound \(\mathrm{C}_{5} \mathrm{H}_{12} ?\)
View solution