Page 334 - Theory and Problems of BEGINNING CHEMISTRY

GLOSSARY 323

reactant element or compound used up in a chemical reaction.
reacting ratio mole ratio in which substances react and are produced, given by the coefficients in the balanced
chemical equation.
reaction a chemical change; a process in which compositions of substances are changed.
reactivity activity; tendency to react.

reagent substance used up in a chemical reaction.
reciprocal key the key on a calculator used to take the reciprocal of a number, that is, to divide the number
into 1. 1/x

redox oxidation reduction.
reducing agent reactant that causes a lowering of the oxidation number of another reactant.
reduction lowering of oxidation number, by gain of (control of ) electrons.
rest mass the mass of a body at rest. (According to Einstein’s theory, a body’s mass will increase as it is put
into motion—as its energy increases—despite its having a constant quantity of matter and thus a constant rest
mass.)

rounding reducing the number of digits in a calculated result to indicate the precision of the measurement(s).

+
−
+
salt a combination of a cation and an anion (except for H ,H 3 O ,O ,orOH ). Salts may be produced by
2−
the reaction of acids and bases.
salt bridge a connector between the two halves of a galvanic cell necessary to complete the circuit and prevent
a charge buildup that would cause stoppage of the current.
saturated hydrocarbon a hydrocarbon containing only single bonds.
saturated solution a solution holding as much solute as it can stably hold at a particular temperature. Solutions
in equilibrium with excess solute are saturated.
scientific notation standard exponential notation.
secondary amine an amine R 2 NH with two and only two R groups.
shell (1) a “layer” of electrons in an atom; (2) a set of electrons all having the same principal quantum number.

shift a change in the position of an equilibrium system. Shift to the left produces reactants from products; shift
to the right produces products from reactants.
SI (Syst`eme International d’Unit´es) a modern version of the metric system.

significant digits significant figures.
significant figures the digits in a measurement or in the calculations resulting from a measurement that indicate
how precisely the measurement was made; significant digits.

single bond a covalent bond with one shared pair of electrons.
solubility the concentration of a saturated solution at a given temperature.
solute substance dissolved in a solvent, such as salt dissolved in water.
solution a homogeneous mixture; a combination of a solvent and solute(s).

solvent substance that dissolves the solute(s).
specific heat the heat capacity per gram of substance; the number of joules required to raise 1 g of substance
◦
1 C.