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  2. Periodic Videos - Wikipedia

    en.wikipedia.org/wiki/Periodic_Videos

    The intent of the videos is to bring chemistry to a new generation of students and to get them enthused about science and understand how chemists think and what chemists are trying to do. [ 9 ] [ 10 ] Many school teachers now incorporate these videos into their classes, [ 4 ] [ 9 ] and the professor has even recorded video responses to some of ...

  3. List of unsolved problems in chemistry - Wikipedia

    en.wikipedia.org/wiki/List_of_unsolved_problems...

    Protein folding problem: Is it possible to predict the secondary, tertiary and quaternary structure of a polypeptide sequence based solely on the sequence and environmental information? Inverse protein-folding problem: Is it possible to design a polypeptide sequence which will adopt a given structure under certain environmental conditions?

  4. Khan Academy - Wikipedia

    en.wikipedia.org/wiki/Khan_Academy

    The Khan Academy website also hosts content from educational YouTube channels and organizations such as Crash Course and the Museum of Modern Art. [30] It also provides online courses for preparing for standardized tests, including the SAT , AP Chemistry , Praxis Core and MCAT [ 31 ] and released LSAT preparation lessons in 2018. [ 32 ]

  5. Stoichiometry - Wikipedia

    en.wikipedia.org/wiki/Stoichiometry

    The reactions may differ in their stoichiometry. For example, the methylation of benzene (C 6 H 6), through a Friedel–Crafts reaction using AlCl 3 as a catalyst, may produce singly methylated (C 6 H 5 CH 3), doubly methylated (C 6 H 4 (CH 3) 2), or still more highly methylated (C 6 H 6−n (CH 3) n) products, as shown in the following example ...

  6. Dissociation constant - Wikipedia

    en.wikipedia.org/wiki/Dissociation_constant

    In chemistry, biochemistry, and pharmacology, a dissociation constant (K D) is a specific type of equilibrium constant that measures the propensity of a larger object to separate (dissociate) reversibly into smaller components, as when a complex falls apart into its component molecules, or when a salt splits up into its component ions.

  7. Atomic ratio - Wikipedia

    en.wikipedia.org/wiki/Atomic_ratio

    The atomic ratio is a measure of the ratio of atoms of one kind (i) to another kind (j). A closely related concept is the atomic percent (or at.% ), which gives the percentage of one kind of atom relative to the total number of atoms. [ 1 ]

  8. Amount of substance - Wikipedia

    en.wikipedia.org/wiki/Amount_of_substance

    In chemistry, the amount of substance (symbol n) in a given sample of matter is defined as a ratio (n = N/N A) between the number of elementary entities (N) and the Avogadro constant (N A). Since 2019, the value of the Avogadro constant N A is defined to be exactly 6.022 140 76 × 10 23 mol −1 .

  9. Trigonometry - Wikipedia

    en.wikipedia.org/wiki/Trigonometry

    Trigonometry (from Ancient Greek τρίγωνον (trígōnon) 'triangle' and μέτρον (métron) 'measure') [1] is a branch of mathematics concerned with relationships between angles and side lengths of triangles.