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– In this topic, we will discuss the Titration Curves in Analytical Chemistry : Definition and Types Titration Curves – An end point is signaled by an observable physical change near the equivalence point of a titration. – The two most widely used signals involve (1) changes in color due …

Gravimetric titrations – Mass (weight) or gravimetric titrations differ from their volumetric counterparts in that the mass of titrant is measured rather than the volume. – Therefore, in a mass titration, a balance and a weighable solution dispenser are substituted for a buret and its markings. – Gravimetric titrations actually …

– In this topic, we will discuss The Areas of the Peaks in NMR Spectroscopy Areas of the Peaks – The area under a peak is proportional to the number of hydrogens contributing to that peak. – For example, in the methyl tert-butyl ether spectrum (Figure 1), the absorption of …

The Number of Signals – In general, the number of NMR signals corresponds to the number of different kinds of protons present in the molecule. – For example, methyl tert-butyl ether has two types of protons (Figure 1). – The three methoxy protons are chemically identical, and they give rise …

– In this topic, we will discuss the colloids: definition, History and Types History of colloids – Thomas Graham (1861) studied the ability of dissolved substances to diffuse into water across a permeable membrane. – He observed that crystalline substances such as sugar, urea, and sodium chloride passed through the …

Some Terms Used in Volumetric Titration – A standard solution (or a standard titrant) is a reagent of known concentration that is used to carry out a volumetric titration. – The volumetric titration is performed by slowly adding a standard solution from a buret or other liquid dispensing device to …

Applications of Gravimetric methods – Gravimetric methods have been developed for most inorganic anions and cations, as well as for such neutral species as water, sulfur dioxide, carbon dioxide, and iodine. – A variety of organic substances can also be determined gravimetrically. – Examples include lactose in milk products, salicylates …

– In this topic, we will discuss the Chemical Shift in 1H NMR Spectroscopy. What is Chemical Shift? – The variations in the positions of NMR absorptions, arising from electronic shielding and deshielding, are called chemical shifts. – Chemical shift is The difference (in parts per million) between the resonance …

– In this topic, we will discuss the Precipitation Gravimetry as an important one of Gravimetric Analysis in analytical chemistry. What is Gravimetric Analysis? – Gravimetric analysis is a method to determine the quantity of an analyte based on the mass of a solid.  – Gravimetric methods of analysis are …

– In this topic, we will discuss Activity coefficients : Definition, Equation, Examples and Properties. Activity Coefficients – Chemists use a term called activity, a, to account for the effects of electrolytes on chemical equilibria. – The activity, or effective concentration, of species X depends on the ionic strength of …

The Effect of Electrolyte on Chemical Equilibria – Experimentally, we find that the position of most solution equilibria depends on the electrolyte concentration of the medium, even when the added electrolyte contains no ion in common with those participating in the equilibrium. – For example, consider again the oxidation of …

What is Analytical Chemistry? Analytical chemistry is what analytical chemists do. – Analytical chemistry is too broad and active a discipline for us to easily or completely define in an introductory textbook. Instead, we will try to say a little about what analytical chemistry is, as well as a little …

– In this topic, we will discuss Acid-Base catalysis: definition, Examples and Mechanism. Acid-Base catalysis – A number of homogeneous catalytic reactions are known which are catalysed by acids or bases, or both acids and bases.  These are often referred to as Acid-Base catalysts. – Arrhenius pointed out that acid …

What happens in an NMR spectrometer? – Before discussing the design of spectrometers, let’s review what happens in an NMR spectrometer. – Protons (in the sample compound) are placed in a magnetic field, where they align either with the field or against it. – While still in the magnetic field, …

– In this topic, we will discuss the Magnetic Shielding by Electrons Magnetic Shielding by Electrons – Up to now, we have considered the resonance of a naked proton in a magnetic field, but real protons in organic compounds are not naked. – They are surrounded by electrons that partially …

Theories of Catalysis – There are two main theories of catalysis: (1) Intermediate Compound Formation theory. (2) The Adsorption theory. – In general, the Intermediate Compound Formation theory applies to homogeneous catalytic reactions and the Adsorption theory applies to heterogeneous catalytic reactions. The Intermediate Compound Formation Theory – The Intermediate …

– In this topic, we will discuss Autocatalysis, Catalytic poisoning and Negative Catalysis. Catalytic poisoning – Very often a heterogeneous catalyst in rendered ineffective by the presence of small amounts of impurities in the reactants. – A substance which destroys the activity of the catalyst to accelerate a reaction, is …

Introduction to NMR  – Nuclear magnetic resonance spectroscopy (NMR) is the most powerful tool available for organic structure determination. – Like infrared spectroscopy, NMR can be used with a very small sample, and it does not harm the  sample. – The NMR spectrum provides a great deal of information about …

– In this topic, we will discuss general Characteristics of Catalytic Reactions and Promoters. General Characteristics of Catalytic Reactions – Although there are different types of catalytic reactions, the following features or characteristics are common to most of them. (1) A catalyst remains unchanged in mass and chemical composition at …

– In this topic, we will discuss the Fragmentation Patterns in Mass Spectrometry. Fragmentation Patterns in Mass Spectrometry – In addition to the molecular formula, the mass spectrum provides structural information. – An electron with a typical energy of 70 eV (6740 kJ mol or 1610 kcal mol) has far …