For test on Chapter 4 Mixtures and compound
Topics and questions for testComposition of MatterLaw of definite proportionsChemical FormulasSeparating MixturesMixtures vs. Compounds• One of the fundamental observations of modern chemistry, the law of definite proportions states that, in Compounds, the elements combine in proportion with each other, by mass.• An equivalent statement is the law of constant composition, which states that all samples of a given chemical compound have the same elemental composition• • Chemists describe compounds using formula in various formats. For molecules, the formula for the molecular unit is shown. For polymeric materials, such as minerals and many metal oxides, the empirical formula is given, e.g. NaCl for table salt. The order of the elements in molecular and empirical formulas is C, then H and then alphabetical. Trifluoroacetic acid is thus described as C2HF3O2. More descriptive formulas convey structure information, illustrated again with trifluoroacetic acid. CF3CO2H. On the other hand, formulas for inorganic compounds often do not convey structural information, as illustrated by H2SO4 for a molecule that has no H-S bonds. A more descriptive presentation would be O2S(OH)2.• A chemical compound is a chemical substance consisting of two or more different chemically bonded chemical elements, with a fixed ratio determining the composition. The ratio of each element is usually expressed by chemical formula. For example, water (H2O) is a compound consisting of two hydrogen atoms bonded to an oxygen atom.• The atoms within a compound can be held together by a variety of interactions, ranging from covalent bonds to electrostatic forces in ionic bonds. A continuum of bond polarities exist between the purely covalent bond (as in H2) and ionic bonds. For example H2O is held together by polar covalent bonds. Sodium chloride is an example of an ionic compound.Do this•How do compounds and mixtures differ?
How do compounds and mixtures differ?
How do covalent and ionic bonds differ?
How do inorganic and organic compounds differ?
What is the rule for chemical formulas?
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