Nitrate is a crucial parameter for assessing water quality, owing to its dual function in ecological systems. These functions can be beneficial or detrimental depending on whether nitrate concentrations are low or high, respectively. The ultraviolet spectrophotometric method (standard as 4500-NO[subscript 3]--B) is a classic method for determining…

This paper describes the implementation of problem-based learning in chemical education with regard to the impact that protolytic reactions have on equilibria. The problem-based task presented here is focused on extremely weak acids and calcuation of the pH value of their aqueous solutions. The task is based on comparisons of K[subscript a] ranges…

A simple mathematical formulation of Mach's principle is given based on a century of investigation into inertia, and used to check the results of Newton's famous bucket experiment.

We present an approximate solution for the downward time of travel in the case of a mass falling with a linear drag force. We show how a quasi-analytical solution implying the Lambert function can be found. We also show that solving the previous problem is equivalent to the search for Wien's displacement law. These results can be of interest for…

We discuss some interesting aspects in the calculation of the electrostatic potential of charge distributions extending to infinity. The presentation is suitable for the advanced undergraduate level. (Contains 3 footnotes.)

We consider the orbit of projectiles launched with arbitrary speeds from the Earth's surface. This is a generalization of Newton's discussion about the transition from parabolic to circular orbits, when the launch speed approaches the value [image omitted]. We find the range for arbitrary launch speeds and angles, and calculate the eccentricity of…

The boiling point of a monofunctional organic compound is expressed as the sum of two parts: a contribution to the boiling point due to the R group and a contribution due to the functional group. The boiling point in absolute temperature of the corresponding RH hydrocarbon is chosen for the contribution to the boiling point of the R group and is a…

We illustrate the derivations of Jeans' criteria for the gravitational instabilities in a static homogeneous Newtonian system for pedagogical objectives. The critical Jeans density surface is presented in terms of dimensionless sound speeds and (characteristic) length scales. (Contains 1 figure.)

Maxwell's equation are solved for an inhomogeneous medium which has a coordinate-dependent dielectric function. The problem and its solutions are given in a format which should make it useful as an intermediate or advanced level problem in an electrodynamics course. (Author/SK)

The students in molecular spectroscopy courses are often required to determine the permitted normal vibrations for linear molecules that belong to particular groups. The reducible group representations generated by the use of Cartesian coordinates can be reduced by the use of a simple algebraic process applied to the group representations. The…

Simple and efficient methods for adding angular momenta and for finding angular momentum eigenstates for systems of equivalent electrons are developed. Several different common representations are used in specific examples. The material is suitable for a graduate course in quantum mechanics. (SK)

Discusses a set of relations (addressing changes in volume and refractivity) for use in the study of binary systems. Suggests including such an experiment in undergraduate physical chemistry courses (measuring density/refractive index of pure compounds and their mixtures) to predict even small changes occurring during mixing process. (Author/JN)

The Poincare group, the group of transformations of the plane which preserve the Minkowski distance between points, is derived as compositions of suitably defined reflections in straight lines. It is shown that any such transformations must be one of four types. (Author/JN)

The general problem of mass accretion by a drop falling through a cloud of droplets is considered as an exercise in introductory or intermediate mechanics. The kinematic behavior of the falling drop is deduced for a variety of mechanisms of mass accretion, and some special limiting conditions are discussed. (Author/SK)

The RKR method for determining accurate potential energy curves is described. Advantages of using the method (compared to Morse procedure) and a TRS-80 computer program which calculates the classical turning points by an RKR method are also described. The computer program is available from the author upon request. (Author/JN)