The widely used method of synthesizing HCl and DCl gases for infrared analysis by hydrolysis of benzoyl chloride includes a potentially dangerous final step whereby the frozen product is allowed to heat and expand into an infrared gas cell. The subsequent rapid rise in vapor pressure can "pop" open glass joints in the vacuum line and vent the…

Discusses ways of teaching the mole concept in high school chemistry classes. Provides resource information on the mole and Avogadro's Number. Includes an explanation of four methods for measuring Avogadro's Number and instructions on how to use the mole. (MA)

Teachers and students alike report difficulties with the measurement unit called mole. This article tries to demonstrate that mole and the corresponding quantity are not exceptional. Mole lacks the context of a given amount because the unit measures the relative number of atoms compared with those present in a standard. Discusses history of…

Investigates HyperCard as a tool for assessment in science education and determines whether or not a HyperCard assessment instrument could differentiate between expert and novice student performance on balancing stoichiometric equations in science education. (ZWH)

The study focuses on percarbonate-based stain removers since the percarbonate can be heated to produce additional sodium carbonate. An experiment that provides general chemistry students an opportunity to apply their knowledge of basic stoichiometry to solve a relevant, real-world problem is described.

Under conditions of constant temperature T and pressure P, chemical equilibrium occurs in a closed system (fixed mass) when the Gibbs free energy G of the reaction mixture is minimized. However, when chemical reactions occur under other conditions, other thermodynamic functions are minimized or maximized. For processes at constant T and volume V,…

The aim of this study is to investigate Emiratii high school students' understandings of stoichiometry, their use of metacognitive strategies, and the influence of students' use of metacognitive strategies on their understandings of stoichiometry. Two instruments were used in this study, the first to measure students' understandings of…

Indicates that the concept of definite proportions or constant composition should be introduced with qualification. Presents arguments against the Law of Definite Proportions and cites examples in the areas of solid solutions, compounds of the transition and inner transition elements, and in some compounds of the representative elements. (GS)

Presents experiments involving the analysis of commercial products such as carbonated beverages and antacids that illustrate the principles of acid-base reactions and present interesting problems in stoichiometry for students. (JRH)

Describes a demonstration of the decomposition of hydrogen peroxide to provide an interesting, quantitative illustration of the stoichiometric relationship between the decomposition of hydrogen peroxide and the formation of oxygen gas. This 10-minute demonstration uses ordinary hydrogen peroxide and yeast that can be purchased in a supermarket.…

A sensor experiment which can be applied to advanced undergraduate laboratory course in physical or analytical chemistry is described along with certain concepts like the demonstration of chemical sensing, preparation of thin films on a substrate, microtitration, optical determination of complex ion stoichiometry and isosbestic point. It is seen…

This study examines Indonesian students' understanding of conservation of matter, balancing of equations and stoichiometry. Eight hundred and sixty-seven Grade 12 students from 22 schools across four different cities in two developed provinces in Indonesia participated in the study. Nineteen teachers also participated in order to validate the…

This two-part series describes the structure of the stoichiometry course at North Carolina State University. The course had a variety of learning objectives, and several nontraditional pedagogies were used in the course delivery. This first paper outlines the course structure and policies, the preparation given to the teaching assistants who…

Discusses an instructional strategy in which stoichiometric reactions are presented in terms of a recipe. Solutions for two different stoichiometric problems are included. (JN)