standard state

(noun)

In chemistry, a reference point used to calculate a material's (pure substance, mixture, or solution) properties under different conditions.

Related Terms

Examples of standard state in the following topics:

  • Standard States and Standard Enthalpy Changes

    • In principle, the choice of standard state is arbitrary, although the International Union of Pure and Applied Chemistry (IUPAC) recommends a conventional set of standard states for general use.
    • Strictly speaking, temperature is not part of the definition of a standard state; the standard state of a gas is conventionally chosen to be 1 bar for an ideal gas, regardless of the temperature.
    • Standard states for atomic elements are given in terms of the most stable allotrope for each element.
    • The standard state should not be confused with standard temperature and pressure (STP) for gases, or with the standard solutions used in analytical chemistry.
    • Standard states are often indicated in textbooks by a circle with a horizontal bar $H^\ominus_f$.

  • Standard Free Energy Changes

    • The concept of standard states is especially important in the case of free energy, so take a moment to review it.
    • For most practical purposes, the following definitions of standard states are acceptable:
    • Don't confuse these thermodynamic standard states with the "standard temperature and pressure" (STP) widely employed in gas law calculations.
    • Recall that the symbol ° refers to the standard state of a substance measured under the conditions of 1 atm pressure or an effective concentration of 1 Molar and a temperature of 298K.
    • The standard Gibbs free energy of formation of a compound is the change of Gibbs free energy that accompanies the formation of 1 mole of that substance from its component elements, at their standard states.

  • Understanding Common Core Standards

    • The Common Core State Standards seek to bring diverse state curricula into alignment with each other, but they are not without controversy.
    • The Common Core State Standards Initiative is a U.S. education initiative that seeks to bring diverse state curricula into alignment with each other by setting academic standards for what students should know and be able to do.
    • Standards were released for mathematics and English language arts in 2010, with a majority of states adopting the standards in the subsequent months.
    • To be eligible, states had to adopt "internationally benchmarked standards and assessments that prepare students for success in college and the work place. " This meant that in order for a state to be eligible for these grants, the states had to adopt the Common Core State Standards or similar career and college readiness standards.
    • Forty-three of the fifty states in the United States are members of the Common Core State Standards Initiative.

  • Common Core Curriculum

    • The Common Core State Standards Initiative is a U.S. education initiative that seeks to bring diverse state curricula into alignment by setting academic standards for what students should know and be able to do.
    • The stated goal of the mathematics standards is to achieve greater focus and coherence in the curriculum.
    • The Common Core State Standards require that standards to be implemented within a "content-rich curriculum," however they do not specify the content that will comprise the curriculum.
    • The Common Core State Standards website explains that some states plan to work together to create a common, universal assessment system based on the common core state standards while other states are choosing to work independently.
    • The Common Core State Standards Initiative is a U.S. education initiative that seeks to bring diverse state curricula into alignment by setting academic standards for what students should know and be able to do.

  • Standard Enthalpy of Reaction

    • The change in enthalpy does not depend upon the particular pathway of a reaction, but only upon the overall energy level of the products and reactants; enthalpy is a state function, and as such, it is additive.
    • In order to calculate the standard enthalpy of a reaction, we can sum up the standard enthalpies of formation of the reactants and subtract this from the sum of the standard enthalpies of formation of the products.
    • Stated mathematically, this gives us:
    • Note that because it exists in its standard state, the standard enthalpy of formation for oxygen gas is 0 kJ/mol.
    • A calculation of standard enthalpy of reaction (∆H°rxn) from standard heats of formation (∆H°f)

  • Standardized Tests

    • In 2001, the United States passed the No Child Left Behind Act, which requires all states to test students in public schools statewide to ensure that they are achieving the desired level of minimum education.
    • Although some states already had statewide standardized testing requirements, for many states, this act required them to create new systems.
    • In 2001, the United States passed the No Child Left Behind Act, which requires all states to test students in public schools statewide to ensure that they are achieving the desired level of minimum education.
    • Although some states already had statewide standardized testing requirements, for many states, this act required them to create new systems.
    • In many places the United States, standardized tests are also used as a graduation requirement.

  • Areas Under Normal Distributions

    • State the proportion of a normal distribution within 1 standard deviation of the mean
    • State the proportion of a normal distribution that is more than 1.96 standard deviations from the mean
    • Normal distribution with a mean of 100 and standard deviation of 20. 68% of the area is within one standard deviation (20) of the mean (100)
    • Normal distribution with a mean of 50 and standard deviation of 10. 68% of the area is within one standard deviation (10) of the mean (50).
    • A normal distribution with a mean of 75 and a standard deviation of 10. 95% of the area is within 1.96 standard deviations of the mean

  • Standard Normal Distribution

    • State the mean and standard deviation of the standard normal distribution
    • A normal distribution with a mean of 0 and a standard deviation of 1 is called a standard normal distribution.
    • Since the distribution has a mean of 0 and a standard deviation of 1, the Z column is equal to the number of standard deviations below (or above) the mean.
    • This process of transforming a distribution to one with a mean of 0 and a standard deviation of 1 is called standardizing the distribution.
    • A portion of a table of the standard normal distribution

  • Anatomical Position

    • Thus, the standard anatomical position provides a "gold standard" when comparing the anatomy of different members of the same species.
    • The standard anatomical position is agreed upon by the international medical community.
    • In humans, the standard anatomical position of the skull is called the Frankfurt plane.
    • It is important to note that all anatomical descriptions are based on the standard anatomical position unless otherwise stated.
    • The regions of the body in standard anatomical position, in which the body is erect.

  • Standard Deviation: Definition and Calculation

    • The average height for adult men in the United States is about 70 inches, with a standard deviation of around 3 inches.
    • This quantity is known as the standard deviation.
    • The sample standard deviation, $s$, is a statistic known as an estimator.
    • As mentioned above, most often the standard deviation is estimated using the corrected sample standard deviation (using $N-1$).
    • Dark blue is one standard deviation on either side of the mean.