General Chemistry

  Experimental  Determination of  Empirical Formulas ** The fact that we can determine the empirical formula of a compound if we know the percent composition enables us to identify compounds experimentally. ** The procedure is as follows.    (1) Chemical analysis tells us the number of grams of each element …

– In this subject, we will discuss Writing and Balancing Chemical Equations. Chemical Reactions and Chemical Equations  – A chemical reaction is a process in which a substance (or substances) is changed into one or more new substances. – To communicate with one another about chemical reactions, chemists have devised …

  Percent Composition of Compounds **As we have seen, the formula of a compound tells us the numbers of atoms of each element in a unit of the compound. ** However, suppose we needed to verify the purity of a compound for use in a laboratory experiment. We could calculate …

  Molecular Mass ** If we know the atomic masses of the component atoms, we can calculate the mass of a molecule. ** The molecular mass: (sometimes called molecular weight) is the sum of the atomic masses (in amu) in the molecule.   ** For example, the molecular mass of …

  Avogadro’s Number (NA) ** Atomic mass units provide a relative scale for the masses of the elements. ** But because atoms have such small masses, no usable scale can be devised to weigh them in calibrated units of atomic mass units. ** In any real situation, we deal with macroscopic …

– In this subject, we will discuss the Atomic Mass and Average Atomic Mass: Definition, Formula, and Calculation Atomic Mass – The mass of an atom depends on the number of electrons, protons, and neutrons it contains. – Knowledge of an atom’s mass is important in laboratory work. – But …

– In this subject, we will discuss the Lewis Structures: Definition, Overview, Structural Formula, Examples Definition of Lewis structures – A Lewis structure is a structural representation of a molecule where dots are used to show electron positions around the atoms and lines or dot pairs represent covalent bonds between …

– In this subject, we will discuss the Nomenclature of Acids, Bases and Hydrates Nomenclature of Acids – An acid can be described as a substance that yields hydrogen ions (H+) when dissolved in water. (H+ is equivalent to one proton, and is often referred to that way.) – Formulas …

How to Name Molecular Compounds – Unlike ionic compounds, Molecular compounds contain discrete molecular units. – They are usually composed of nonmetallic elements. – Many molecular compounds are binary compounds. – Naming binary molecular compounds is similar to naming binary ionic compounds. – We place the name of the first …

– In this subject, we will discuss the Nomenclature of Ionic Compounds. Naming Compounds – In addition to using formulas to show the composition of molecules and compounds, chemists have developed a system for naming substances based on their composition. – we divided naming substances into three categories: (1) Nomenclature of …

– In this subject, we will discuss Molecular Formulas and Empirical Formulas: Definitions, Examples – Chemists use Chemical formulas to express the composition of molecules and ionic compounds in terms of chemical symbols. – By composition we mean not only the elements present but also the ratios in which the atoms …

– In this subject, we will discuss the Atoms, Molecules, and Ions: Definition, Types, Examples Atoms – Of all the elements, only the six noble gases in Group 8A of the periodic table (He, Ne, Ar, Kr, Xe, and Rn) exist in nature as single atoms. – For this reason, …

– In this subject, we will discuss the Atomic Number, Mass Number, and Isotopes: Definition, Formula, and Calculation Atomic number – All atoms can be identified by the number of protons and neutrons they contain. – The number of protons in the nucleus of each atom of an element is …

  Equations of State for Ideal gas ** Phenomenological thermodynamics is based on experiment, on measurements that you might make in a lab, garage, or kitchen. ** For example, for any fixed amount of a pure gas, two state variables are pressure, p, and volume, V. Each can be controlled …

– In this subject, we will discuss Calculating the pH of Weak Acid and Base Solutions Total and partial ionization – When an acid or base is dissolved in water, it will dissociate, or ionize According to the equations:  – The amount of ionization is dependent on the strength of …

– In this subject, we will discuss the pH Scale: Definition, formula, Notes, Solved problems  pH Scale – The concentration of H+ or OH− in aqueous solution can vary over extremely wide ranges, from 1 M or greater to 10−14 M or less. – To construct a plot of H+ concentration against some variable …

– In this subject, we will discuss Acid-Base Equilibrium in Water. Acid-Base Equilibrium in Water – When an acid or base is dissolved in water, it will dissociate, or ionize According to the equations:  – The amount of ionization is dependent on the strength of the acid or the base. …

– In this subject, we will discuss Acid-Base Theories: Arrhenius, Lewis, and Bronsted-Lowry Theory Acid-base Theories – Several acid–base theories have been proposed to explain or classify acidic and basic properties of substances. – You are probably most familiar with the Arrhenius theory, which applies only to water. – Other …

– In this subject, we will discuss The Equipment and Manipulations Associated with weighing. Weighing Equipment and Manipulations – The mass of many solids changes with humidity because they tend to absorb weighable amounts of moisture. – This effect is especially pronounced when a large surface area is exposed, as …

– In this subject, we will discuss the Discovery of the Atom, Nucleus, electron, Proton, and Neutron Definition of atom – Based on Dalton’s atomic theory, we can define an atom as the basic unit of an element that can enter into a chemical combination. – Dalton imagined an atom …