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Chapter 15: Problem 72

One of the tests used to detect the presence of LSD or some of the other psilocybin-like alkaloids often found in psychedelic mushrooms is the Ehrlich test. For this test a solution of \(p\) dimethylaminobenzaldehyde, \(\mathrm{C}_{9} \mathrm{H}_{11} \mathrm{NO}\), in \(3.25 \mathrm{M} \mathrm{HCI}\) is used to detect the presence of any of these compounds. How many \(\mathrm{mL}\) of concentrated \(\mathrm{HCI}(12.1 M)\) are required to make \(3.00 \mathrm{~L}\) of \(3.25 \mathrm{MHCI}\) for preparing Ehrlich reagent?

Short Answer

Expert verified
Approximately 806.6 mL of concentrated HCl are required.

Step by step solution

01

Understand the problem

The goal is to find out how many milliliters of a concentrated HCl solution (12.1 M) are needed to prepare 3.00 liters of a 3.25 M HCl solution.
02

Use the dilution formula

The dilution formula relates the concentrations and volumes of the stock solution and the diluted solution: \( C_1 V_1 = C_2 V_2 \).Where, \( C_1 \) is the concentration of the stock solution (12.1 M), \( V_1 \) is the volume of the stock solution to be found, \( C_2 \) is the concentration of the diluted solution (3.25 M), \( V_2 \) is the volume of the diluted solution (3.00 L).
03

Substitute the values into the dilution formula

Substitute \( C_1 = 12.1 \) M, \( C_2 = 3.25 \) M, and \( V_2 = 3.00 \) L into the formula: \( 12.1 V_1 = 3.25 \times 3.00 \). This simplifies to: \( 12.1 V_1 = 9.75 \).
04

Solve for \( V_1 \)

Divide both sides of the equation by 12.1 to find \( V_1 \): \( V_1 = \frac{9.75}{12.1} \). Calculating this gives: \( V_1 \approx 0.8066 \) liters.
05

Convert the volume to milliliters

Convert 0.8066 liters to milliliters by multiplying by 1000: \( 0.8066 \times 1000 = 806.6 \) mL.

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Key Concepts

These are the key concepts you need to understand to accurately answer the question.

Dilution Formula
The dilution formula is a key equation in chemistry used to determine the amount of a concentrated solution required to prepare a dilute solution. The formula is expressed as: \( C_1V_1 = C_2V_2 \).
This equation shows that the product of the concentration (\(C_1\)) and volume (\(V_1\)) of the stock solution is equal to the product of the concentration (\(C_2\)) and volume (\(V_2\)) of the diluted solution.
To use this formula, just plug in the known values, and solve for the unknown variable.
Molarity
Molarity (\(M\)) is a measure of the concentration of a solute in a solution. It is defined as the number of moles of solute per liter of solution. The formula for calculating molarity is: \[M = \frac{moles \,of \,solute}{liters \,of \,solution}\].
Molarity is important when performing dilution calculations because it allows you to relate the concentration of the initial solution to the diluted solution.
In the given exercise, the initial molarity is 12.1 M, and the final molarity is 3.25 M. Knowing these values allows us to determine how much concentrate is needed.
Solution Preparation
Preparing a solution involves mixing a solute with a solvent to achieve the desired concentration.
To prepare a solution accurately, it's important to use the dilution formula to calculate the amount of solute or concentrated solution needed.
For the Ehrlich test, we need to prepare 3.00 liters of 3.25 M HCl solution from a concentrated 12.1 M HCl stock solution. Knowing this, we use the dilution formula to find the volume of the stock solution required to achieve the final concentration.
Chemical Concentrations
Chemical concentrations indicate how much solute is present in a given volume of solution.
Common units for concentration include molarity, weight percent, and molality, but molarity is most widely used in chemistry.
In the exercise, concentration values are given in molarity (M), which simplifies the calculation using the dilution formula. By focusing on molar concentrations, we can easily determine the volume of the concentrated solution needed to prepare a specific volume of diluted solution with the desired concentration.
Ehrlich Test
The Ehrlich test is a chemical test used to detect the presence of certain compounds, such as LSD and psilocybin-like alkaloids in psychedelic mushrooms.
The test uses a reagent solution of p-dimethylaminobenzaldehyde in HCl. To prepare this reagent, it's crucial to accurately dilute a concentrated HCl solution to the desired molarity.
In this exercise, we prepare the 3.25 M HCl solution needed for the test by calculating how much of the concentrated 12.1 M HCl stock solution we need using the dilution formula.

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Most popular questions from this chapter

Two drops \((0.1 \mathrm{~mL})\) of \(1.0 \mathrm{M} \mathrm{HCl}\) are added to water to make \(1.0 \mathrm{~L}\) of solution. What is the \(\mathrm{pH}\) of this solution if the \(\mathrm{HCl}\) is \(100 \%\) ionized?

In an acid-base titration, \(25.22 \mathrm{~mL}\) of \(\mathrm{H}_{2} \mathrm{SO}_{4}\) were used to neutralize \(35.22 \mathrm{~mL}\) of \(0.313 \mathrm{M} \mathrm{NaOH}\). What was the molarity of the \(\mathrm{H}_{2} \mathrm{SO}_{4}\) solution? $$ \mathrm{H}_{2} \mathrm{SO}_{4}+2 \mathrm{NaOH} \longrightarrow \mathrm{Na}_{2} \mathrm{SO}_{4}+2 \mathrm{H}_{2} \mathrm{O} $$

What volume of \(\mathrm{H}_{2}\) gas, measured at \(27^{\circ} \mathrm{C}\) and 700 . torr, can be obtained by reacting \(5.00 \mathrm{~g}\) of zinc metal with \(100 . \mathrm{mL}\) of \(0.350\) \(M \mathrm{HCl}\) ? The equation is $$ \mathrm{Zn}(s)+2 \mathrm{HCl}(a q) \longrightarrow \mathrm{ZnCl}_{2}(a q)+\mathrm{H}_{2}(g) $$

For each of the given pairs, determine which solution is more acidic. All are water solutions. Explain your answer. (a) \(1 M \mathrm{HCl}\) or \(1 M \mathrm{H}_{2} \mathrm{SO}_{4}\) ? (b) \(1 \mathrm{M} \mathrm{HCl}\) or \(1 M \mathrm{HC}_{2} \mathrm{H}_{3} \mathrm{O}_{2}\) ?

If \(380 \mathrm{~mL}\) of \(0.35 \mathrm{M} \mathrm{Ba}(\mathrm{OH})_{2}\) are added to 500 . \(\mathrm{mL}\) of \(0.65\) \(M \mathrm{HCl}\), will the mixture be acidic or basic? Find the \(\mathrm{pH}\) of the resulting solution.
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