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Analytical Chemistry - Calibration

Analytical Chemistry - Calibration Home > Analytical Chemistry > Calibration CALIBRATION What is calibration? Calibrated instruments|Analytical Chemistry Calibrating a pH meter using buffers Quantitative Analysis by Atomic Absorption Performance Verification of Analytical Balances according to ISO/IEC 17025 Calibration and Outliers - Statistical Analysis Calibration of an instrument in Analytical Chemistry is the operation that determines the functional relationship between measured values (signal intensities S at certain signal positions zi) and analytical quantities characterizing types of analytes qi and their amount ( content , concentration ) n. Calibration includes the selection of the model (its functional form), the estimation of the model parameters as well as the errors, and their validation. During calibration , the in...
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Carbocations: Factors affecting their Stability

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A carbocation is a species where a carbon atom bonds to three carbon atoms and has a positive charge. Carbocations are electron deficient species and therefore very reactive and unstable . Anything which donates electron density to the electron-deficient center will help to stabilize them. Factors that stabilize them are the following:  Neighboring carbon atoms (inductive effect) Neighboring carbon-carbon multiple bonds (resonance effect) Neighboring atoms with lone pairs (resonance effect) How carbocations are stabilized by neighboring carbons atoms? The stability of carbocations decreases as the number of carbons attached to the C+ decreases. That means that tertiary carbocations are more stable than secondary that in turn are more stable than primary (Fig. 1). Fig. 1: Carbocation stability increases as methyl substitution increases around the electron deficient carbon C+. The methyl groups (-CH 3 ) are electron donating and therefore stabilize the positive charge (inductive ...
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How to determine the order of a reaction by the initial rates method?

How to determine the order of a reaction? Determining the form of the Rate Law (Order of Reaction) by the method of Initial Rates Home > Rate of a Chemical Reaction - Chemical Kinetics > Rates of Chemical Reactions and the Collision Model > How to determine the order of a reaction by the initial rates method?   How to determine the order of a reaction by the initial rates method?   A rate law is an expression which shows how the rate of a reaction depends on the concentrations of reactants. For the decomposition of NO 2 we can write: 2NO 2 (g) → 2NO(g) + O 2 (g)  Rate = k [NO 2 ] n      (Rate Law) k is the rate constant and n is the order of reaction (n can be positive or negative, integer or fraction) Both k and n must be determined experimentally. For the general reaction: aA + bB → cC + dD   (1) the rate law is given by:   Rate = k. [A] m [B] n     (2)   There are two types of rate laws: The differential rat...
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