Q: During the titration of a commercial antacid, a student uses 0.0250 L of 0.100 M HCl to neutralize the antacid. How many moles of HCl were used?

$$n = M \times V = 0.100 \times 0.0250 = 0.00250$$ \text{ mol}$

Q: A student is performing a buffer titration using acetic acid and sodium acetate. Which equation best describes the relationship between pH, pKa, and the concentrations of acid and conjugate base?

$$\text{pH} = \text{p}K_a + \log \left( \frac{[\text{A}^-]}{[\text{HA}]} \right)$$

Q: A student is asked to calculate the percent error for a mass measurement. If the accepted value is 2.50 g and the measured value is 2.40 g, what is the percent error?

$$\text{Percent Error} = \frac{|2.50 - 2.40|}{2.50} \times 100\% = 4.0\%$$

Q: A student is preparing a solution by dissolving 5.00 g of NaCl in enough water to make 250 mL of solution. What is the molarity of the solution? (Molar mass of NaCl = 58.44 g/mol)

$$M = \frac{5.00}{58.44 \times 0.250} = 0.342 M$$

Question 1

A student is performing a spectrophotometric determination of iron in a vitamin tablet. If the absorbance measured is 0.650 and the calibration curve equation is $$A = 0.200 + 1.50C$$, where $$A is $$absorbance and $$C is $$concentration in mol/L, what is the concentration of iron in the sample?

Accepted Answer

$$C = \frac{0.650 - 0.200}{1.50} = 0.300$$ mol/L

Question 2

During the titration of a commercial antacid, a student uses 0.0250 L of 0.100 M HCl to neutralize the antacid. How many moles of HCl were used?

Accepted Answer

$$n = M 	imes V = 0.100 	imes 0.0250 = 0.00250$$ 	ext{ mol}$

Question 3

Which of the following best describes the purpose of a calibration curve in quantitative chemical analysis?

Accepted Answer

To determine the relationship between instrument response and analyte concentration

Question 4

A student is analyzing the kinetics of the reaction between crystal violet and sodium hydroxide. If the rate law is $$	ext{Rate} = k[CV]^1[OH^-]^0$$, what is the order of the reaction with respect to sodium hydroxide?

Accepted Answer

Zero order

Question 5

In a system at equilibrium, which of the following statements is TRUE?

Accepted Answer

The rates of the forward and reverse reactions are equal

Question 6

A student is asked to calculate the equilibrium constant $$K_c$$ for a reaction where $$[A] = 0.20 M$$, $$[B] = 0.10 M$$, and the balanced equation is $$A \rightleftharpoons 2B. $$What is the correct expression for $$K_c$$?

Accepted Answer

$$K_c = \frac{[B]^2}{[A]}$$

Question 7

During a qualitative analysis of cations, a student observes a precipitate when adding NaCl to a solution. Which cation is most likely present?

Accepted Answer

Ag$$^+$$

Question 8

A student is performing a buffer titration using acetic acid and sodium acetate. Which equation best describes the relationship between pH, pKa, and the concentrations of acid and conjugate base?

Accepted Answer

$$	ext{pH} = 	ext{p}K_a + \log \left( \frac{[	ext{A}^-]}{[	ext{HA}]} ight)$$

Question 9

In the experiment to determine the vitamin C content in orange juice, which chemical property of vitamin C is most important for its quantitative analysis?

Accepted Answer

Its ability to act as a reducing agent

Question 10

A student is asked to calculate the percent error for a mass measurement. If the accepted value is 2.50 g and the measured value is 2.40 g, what is the percent error?

Accepted Answer

$$	ext{Percent Error} = \frac{|2.50 - 2.40|}{2.50} 	imes 100\% = 4.0\%$$

Question 11

Which of the following is a correct safety practice when performing laboratory experiments?

Accepted Answer

Always wear safety goggles and a lab coat during experiments

Question 12

A student is preparing a solution by dissolving 5.00 g of NaCl in enough water to make 250 mL of solution. What is the molarity of the solution? (Molar mass of NaCl = 58.44 g/mol)

Accepted Answer

$$M = \frac{5.00}{58.44 	imes 0.250} = 0.342 M$$

Question 13

In a calorimetry experiment, a student mixes 50.0 g of water at 25.0°C with 50.0 g of water at 75.0°C. Assuming no heat loss, what is the final temperature of the mixture?

Accepted Answer

50.0°C

Question 14

A student is analyzing a system in equilibrium. If more reactant is added, what will happen according to Le Chatelier's Principle?

Accepted Answer

The equilibrium will shift toward the products

Question 15

Which of the following is the best reason for using a scientific notebook in laboratory experiments?

Accepted Answer

To provide a permanent, accurate record of experimental procedures and results

Question 16

A student is performing a qualitative analysis and observes a deep blue color upon adding ammonia to a solution containing copper(II) ions. What complex ion is formed?

Accepted Answer

[Cu(NH$$_3$$)$$_4$$]$$^{2+}$$

Question 17

In the experiment involving the titration of vitamin C, which indicator is commonly used to detect the endpoint?

Accepted Answer

Starch

Question 18

A student is asked to calculate the energy change in a calorimetry experiment. If 100 g of water absorbs 836 J of heat, what is the temperature change? (Specific heat of water = 4.18 J/g°C)

Accepted Answer

$$\Delta T = \frac{836}{100 	imes 4.18} = 2.00^\circ 	ext{C}$$

Question 19

Which of the following is a correct statement about the qualitative analysis of anions?

Accepted Answer

The presence of sulfate ions can be confirmed by the formation of a white precipitate with barium chloride

CHE 118 General Chemistry II Laboratory Syllabus – Key Topics and Study Guide

Guida di studio - Domande di pratica

Study guide - Flashcard