5. Determining the Number of Atoms or Ions in a Substance

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Equilibrium : CommonIonEffect (9 Variations)
The molar solubility of lead(II) fluoride (PbF_{2}) is
2.1 x 10^{-3} mol/L in pure water at 25^{o}C. What is the molar solubility of lead(II) fluoride in 0.10 M NaF at 25^{o}C? (Assume that the only relevant reaction is the solubility-product equilibrium.)

Equilibrium |

Chemometrics

Equilibrium : ConcFromKsp (8 Variations)
The K_{sp} of BaF_{2} is
1.7 x 10^{-6} mol/L in water at 25^{o}C. What is the concentration of barium ions in equilibrium with solid barium fluoride? (Assume that the only relevant reaction is the solubility-product equilibrium.)

Those Baffling SubscriptsArthur W. Friedel and David P. Maloney Study of the difficulties students have in interpreting subscripts correctly and distinguishing atoms from molecules when answering questions and solving problems. Friedel, Arthur W.; Maloney, David P. J. Chem. Educ.1995, 72, 899.

Nomenclature / Units / Symbols |

Stoichiometry |

Chemometrics

A mole of M&M's Merlo, Carmela; Turner, Kathleen E. Engaging students by asking the question: How thick would the layer of M&M candies be if we covered the continental United States with a mole of these candies? Compare this to a mole of water. Merlo, Carmela; Turner, Kathleen E. J. Chem. Educ.1993, 70, 453.

Stoichiometry |

Chemometrics

Measuring Avogadro's number on the overhead projector Solomon, Sally; Hur, Chinhyu A Petri dish filled with water and stearic acid dissolved in petroleum ether upon an overhead projector can be used to introduce the topic of Avogadro's number. Solomon, Sally; Hur, Chinhyu J. Chem. Educ.1993, 70, 252.

Visualizing Numerical Methods (2)William F. Coleman These movies are designed to help students visualize various numerical approaches to evaluating functions or solving equations. The methods themselves may be familiar to students from their mathematics courses, but they may have forgotten the material or never made the connection between a statement such as "the derivative of a curve at a given point is the slope of the line tangent to the curve at that point" and the way that one might evaluate such a derivative. All of the movies have VCR-style controls that enable the student to step through them one frame at a time and to move backwards as well as forwards.

Chemometrics

A Method of Visual Interactive RegressionMichelle S. Kim, Maureen Burkart, Myung-Hoon Kim Over the past decade many colleges and universities have placed increased emphasis on having students develop statistical and data analysis skills in a range of disciplines. Some institutions now require that all students complete at least one course with a strong component of data analysis, whether the data are from chemical experiments, the census, or some other source. As chemists, one of our concerns should be to ensure that students view data analysis as an integral part of any quantitative experiment, and, as far as possible, do not treat this process as a black box. The authors of A Method of Visual Interactive Regression, a spreadsheet application, have developed a visual approach to linear least-squares curve fitting that drives home the idea of minimizing the sum of the squares of the deviations in order to find the best fit to a set of data that are being described by a linear relationship. For many students these visualizations are likely to persist a great deal longer than the mathematical derivations of the equation for the slope and the intercept. The visualizations will provide a useful connection between a set of equations and the buttons on a calculator or the insertion of a trendline in a spreadsheet.