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  2. Empirical formula - Wikipedia

    en.wikipedia.org/wiki/Empirical_formula

    Glucose (C 6 H 12 O 6), ribose (C 5 H 10 O 5), Acetic acid (C 2 H 4 O 2), and formaldehyde (CH 2 O) all have different molecular formulas but the same empirical formula: CH 2 O.This is the actual molecular formula for formaldehyde, but acetic acid has double the number of atoms, ribose has five times the number of atoms, and glucose has six times the number of atoms.

  3. Formula - Wikipedia

    en.wikipedia.org/wiki/Formula

    A molecular formula enumerates the number of atoms to reflect those in the molecule, so that the molecular formula for glucose is C 6 H 12 O 6 rather than the glucose empirical formula, which is CH 2 O. Except for the very simple substances, molecular chemical formulas generally lack needed structural information, and might even be ambiguous in ...

  4. Mass fraction (chemistry) - Wikipedia

    en.wikipedia.org/wiki/Mass_fraction_(chemistry)

    In chemistry, the mass fraction of a substance within a mixture is the ratio (alternatively denoted ) of the mass of that substance to the total mass of the mixture. [1] ...

  5. Chemical formula - Wikipedia

    en.wikipedia.org/wiki/Chemical_formula

    An example of the difference is the empirical formula for glucose, which is CH 2 O (ratio 1:2:1), while its molecular formula is C 6 H 12 O 6 (number of atoms 6:12:6). For water, both formulae are H 2 O. A molecular formula provides more information about a molecule than its empirical formula, but is more difficult to establish.

  6. Arrhenius equation - Wikipedia

    en.wikipedia.org/wiki/Arrhenius_equation

    In physical chemistry, the Arrhenius equation is a formula for the temperature dependence of reaction rates.The equation was proposed by Svante Arrhenius in 1889, based on the work of Dutch chemist Jacobus Henricus van 't Hoff who had noted in 1884 that the van 't Hoff equation for the temperature dependence of equilibrium constants suggests such a formula for the rates of both forward and ...

  7. Formula unit - Wikipedia

    en.wikipedia.org/wiki/Formula_unit

    In most cases the formula representing a formula unit will also be an empirical formula, such as calcium carbonate (CaCO 3) or sodium chloride (NaCl), but it is not always the case. For example, the ionic compounds potassium persulfate ( K 2 S 2 O 8 ), mercury(I) nitrate Hg 2 (NO 3 ) 2 , and sodium peroxide Na 2 O 2 , have empirical formulas of ...

  8. 68–95–99.7 rule - Wikipedia

    en.wikipedia.org/wiki/68–95–99.7_rule

    In statistics, the 68–95–99.7 rule, also known as the empirical rule, and sometimes abbreviated 3sr, is a shorthand used to remember the percentage of values that lie within an interval estimate in a normal distribution: approximately 68%, 95%, and 99.7% of the values lie within one, two, and three standard deviations of the mean, respectively.

  9. Sample mean and covariance - Wikipedia

    en.wikipedia.org/wiki/Sample_mean_and_covariance

    The sample mean is the average of the values of a variable in a sample, which is the sum of those values divided by the number of values. Using mathematical notation, if a sample of N observations on variable X is taken from the population, the sample mean is: