# Resource Type: Tutorials

ChemCollective tutorials walk students through solving chemistry problems movies, text, and interactive tutors. Because the hints given by these tutors ultimately provide the solution to the problem, they are similar to worked examples in a textbook. Currently, we have tutorials covering concepts in stoichiometry, buffers, and equilibrium.

• ## Stoichiometry

### The Mole, Molarity, and Density

• #### The Mole

This tutorial introduces the concept of the mole and how it is used in chemistry to connect macroscopic and molecular level scales. Practice is provided on the applied definition of the mole.

• #### Significant Figures

This tutorial provides a brief review of the guides for determining how many significant figures to include when reporting your answer in a chemistry calculation. Guided practice in performing significant figures…

• #### Dimensional Analysis/Stoichiometric Conversions

This tutorial provides a brief overview of dimensional analysis, including conversion between the amount of a substance expressed in "number of molecules" and the amount of a substance expressed in "moles of molecules".

• #### Calculating Molecular Weight

This tutorial provides instruction and practice on how to calculate the molecular weight of a substance from the atomic weights given on the periodic table.

• #### Using Molecular Weight

This tutorial explains use the molecular weight to convert between the macroscopic scale (grams of a substance) and the microscopic scale (number of molecules of that substance). Guided practice performing molecular…

• #### Composition Stoichiometry

This tutorial provides instruction and practice converting between moles of a molecule and the moles of atoms that the molecule is composed of.

• #### Solution Stoichiometry (Molarity)

This tutorial provides a quantitative overview of substances in solution and practice quantifying the amount of a substance in a solution. Guided practice in solution concentration calculations is provided.

• #### Measuring Density

This tutorial explains the definition of density and explains how to perform density measurements. Guided practice in density calculations is also provided.

• #### Making a Standard Solution from Another Solution: Dilution

This tutorial begins with the concept of concentration and expands this to the concept of dilution. It then provides and overview of the calculations and procedure for performing a dilution in the laboratory. Guided…

• ### Reaction Stoichiometry and Limiting Reagents

• #### Reaction Stoichiometry

This tutorial introduces the concept of reaction stoichiometry, determining the amount of substance that is consumed or produced by a reaction. The tutorial then explains how to calculate how much of a reactant…

• #### The Stoichiometry of Product Formation and Percent Yield

This tutorial provides on overview in determining the amount of product formed by a reaction. It explains how to perform calculations involving how much product was formed in a chemical reaction and explains theoretical…

• #### Limiting Reagents

This tutorial describes how to determine the amount of each reactant that is consumed and each product that is produced in a given chemical reaction. Guided problems as well as a randomized calculation activity…

• ### Empirical Formula and Mixtures

• #### Empirical Formula Introduction

This tutorial defines empirical formula and discusses various ways in which it is used.

• #### Determining the Empirical Formula of a Compund from Its Molecular Formula

This tutorial explains how to calculate an empirical formula when given a molecular formula. Guided practice in performing empirical formula calculations from molecular weight is provided.

• #### Determining the Empirical Formula from an Elemental Analysis

This tutorial explains how to obtain a substance’s the empirical formula from an elemental analysis. It discusses how to compare the empirical formula obtained from an elemental analysis with that from a molecular…

• #### Composition of Mixtures

This tutorial explains the advanced topic of using a chemical reaction, such as burning in oxygen, to determine the relative composition of a mixture. Guided practice in performing calculations that involve a mixture…

• ## Thermochemistry

### Energy and Enthalpy

• #### Entropy and free energy

This tutorial uses animations and simulations to explain free energy and entropy. Part of an interdisciplinary project developed at Carnegie Mellon, MIT and Kent State.

• ### Entropy

• #### Entropy and free energy

This tutorial uses animations and simulations to explain free energy and entropy. Part of an interdisciplinary project developed at Carnegie Mellon, MIT and Kent State.

• ## Kinetics

### Mechanistic Kinetics

• #### Kinetics of Food Dyes

Students carry out and interpret experiments that use a UV/VIS spectrometer to monitor the bleaching of dye. Includes instruction on Beer’s law and analysis of kinetic traces.

• ## Equilibrium

### LeChatlier's Principle

• #### Concentration

Discusses how LeChatelier's principle applies when the "stress" to a system at equilibrium is a change in concentration of products or reactants.

• #### LeChatlier's Principle: Hemoglobin scenario

Chemists use LeChatelier's principle to reason qualitatively about the influence of changes in concentration, temperature or pressure on systems that are at equilibrium. This movie describes the hemoglobin scenario…

• #### Using LeChatlier's Principle

Introduces the general formulation of Le Chatlier's principle. LeChatlier's principle is a general and very powerful framework for making predictions about the effects of stress is on chemical systems.

• #### Reversible Reactions

Gives a more general overview of reversible reactions and the concept of chemical equilibrium.

• #### Temperature

LeChatelier's principle is used to determine the response of a system at chemical equilibrium to an applied stress. This tutorial looks at how changes in temperature influence systems at equilibrium.

• #### Volume/Pressure

LeChatelier's principle is a qualitative approach to reason about how systems at equilibrium will react to changes. This tutorial looks at how changes in volume or pressure influence systems at equilibrium.

• ### Progress of Reaction

• #### Comparing Q to K to determine shift

If a system has not reached chemical equilibrium, we can use the reaction quotient, Q, and the equilibrium constant, K to determine whether the reaction will shift towards products (right) or reactants (left).

• #### Equilibrium is dynamic

Once a system has reached chemical equilibrium, reactions still occur. Equilibrium systems are dynamic. Although the concentrations have reached a steady state, both the forward and reverse reactions continue to…

• #### Comparing Q to K Tutorial: Hemoglobin scenario

In this movie, we describe the hemoglobin scenario from the perspective of comparing Q (a measure of the current state of a reaction) to K (a measure of the equilibrium state of a reaction).

• #### Law of mass action (Q=K)

Chemical equilibrium systems obey the law of mass action. This law states that the reaction quotient, Q, will be equal to a constant when a system reaches chemical equilibrium. This tutorial explains the law of…

• #### Manipulating K and chemical reactions

This tutorial looks at how Q and K change when we manipulate a chemical reaction by doubling it, reversing it, or combining it with another reaction.

• #### Progress of reaction (Q)

A central concept that underlies all of the reasoning we will be doing about chemical equilibrium systems is the progress of reaction.This tutorial defines and examines the progress of reaction.

• #### Q for heterogeneous reactions

This tutorial discusses how to determine which concentrations appear in the law of mass action when calculating the reaction quotient Q.

• #### Equilibrium and thermodynamics (K and ΔG)

This tutorial looks at the relation between the equilibrium state reached by reversible reactions and the thermodynamics of those reactions.

• ### Equilibrium Calculations

• #### Quantitative Equilibrium: Hemoglobin scenario

This movie describes the hemoglobin scenario from the perspective of quantitative calculations.

• #### Calculations for intermediate values of K

How do we determine final concentrations for equilibrium systems? When reactions are reversible, neither the forward nor the backward reaction will progress to completion. This page demonstrates quantitative calculations…

• #### Calculations for large or small values of K

Many reversible reactions have large or small values for their equilibrium constant, K. That is, one reaction (either the forward or the reverse) is much stronger than the other reaction. For instance, most…

• #### Limiting reagents using ICE tables

This tutorial demonstrates quantitative calculations to determine final concentrations in reactions that go to completion.

• #### Overview (Equilibrium vs. limiting reagents)

A general introduction to a number of techniques used to determine how chemical reactions alter the concentrations of chemical species.

• #### Shifting starting position to simplify calculations

Quantitative calculations on chemical equilibrium systems often lead to rather tedious algebra involving cubic or high-order polynomial equations. Since all possible states of a chemical reaction (e.g., values…

• ## Acid-Base Chemistry

### Buffer Solutions

• #### pH and Buffers Defined

This tutorial presents a review of the definitions for pH and buffer solutions

• #### pH in the Absence of a Buffer

This tutorial describes the effects of adding strong base or strong acid to water.

• #### How Buffers Work

This tutorial describes how buffers protect against pH changes when strong acid or base is added.

• #### Creating a buffer from a weak acid and a strong base (Walkthrough activity)

This set of problems and tutored examples walks students through calculating the amount weak acid and a strong base needed to create a buffer solution with a specific concentration.

• #### Predicting the pH of a Buffer

This tutorial describes the calculations for determining the pH of a buffer solution.

• #### Determining the pH of a buffer solution (Walkthrough activity)

This set of problems and tutored examples walks students through calculating the pH of a buffer.

• #### Determining the pH of a buffer solution after addition of NaOH (Walkthrough activity)

This set of problems and tutored examples walks students through calculating the pH of a buffer after a strong base has been added

• #### Buffer Capacity

This tutorial describes the concept of the effectiveness of a buffer’s ability to offset the effects of adding a strong acid or base on the pH of a system.

• #### Determining the buffer capacity for addition of a strong base (Walkthrough activity)

This set of problems and tutored examples walks students through calculating the buffer capacity of a buffer when strong base is added.

• #### Relation of buffer capacity to concentration of buffering agents (Walkthrough activity)

This set of problems and tutored examples walks students through calculating a buffer’s capacity and initial concentration when strong acid is added.

• ## Oxidation/Reduction and Electrochemistry

### Galvanic Cells

• #### Electrochemistry: Galvanic Cells and the Nernst Equation

Students first develop their own activity series, based on pictures of metals immersed in various solutions. A simulation of an electrochemical cell then provides practice with both standard and nonstandard cells.