Mastering Chemistry Help

The energy producing cells are of two types - primary cells and secondary cells. 1) Primary cells In a primary cell the reaction occurs only once and it becomes dead after a period of time and hence cannot be used again. Dry cell, mercury cell etc are examples of primary cells. Dry cell The anode is zinc vessel and the cathode rod. It is surrounded by powdered Mno2. The space between the electrode is filled with a paste of NH4Cl and ZnCl2, the electrolyte. The potential is 1.5 V Zn ------> Zn2+ + 2 electron (anode) NH4+ + MnO2 + electron ------> MnO(OH) + NH3 (cathode) It is of our common experience that dry cells do not have a long life. It is because the acidic ammonium chloride corrodes the zinc container even if the acidic ammonium chloride corrodes the zinc container even if the cell is not in use. In the leak proof cells, the zinc vessel is protected by an outer steel covering. In these cells recharging is not possible. 2) Secondary cells These are cells which can be...

The enzymes are acting as catalysts due to the presence of certain specific regions on their surface, called active sites or catalytic sites. Two models have been proposed for enzyme action. Lock and Key model The active site of a given enzyme is so shaped that only its specific substrates fit into it. We can compare substrate or reactant molecule to the key and active site to the lock. Induced-fit model Modern X-ray crystallographic and spectroscopic methods show that in many cases the enzyme changes shape when the substrate lands at the active site. This induced fit model of enzyme action pictures the substrate inducing the active site to adopt a perfect fit, rather than a rigidly shaped lock and key. We can explain the mechanism of enzyme action using the transition state theory or the intermediate compound formation theory. It involves the following steps. 1) The reactant molecules bind to a region on the surface of the enzyme called active site which results in the formation of...

Bio polymers Biopolymers are a special class of polymers found in nature, starch, protein and peptides. DNA and RNA are all examples of biopolymers, in which monomer unit, respectively are sugars, amino acids and nucleic acids. A major difference between biopolymers and polymers can be found in their structures. Bio polymers inherently have a well defined structure. Many biopolymers spontaneously "Fold" in to characteristic shapes, which determine their biological functions and depend in a complicated way on their primary structures. Structural biology is the study of the shapes of biopolymers. In contrast most synthetic structures have much simpler and mere random or statistic structures. Another important difference is the lack of a molecular mass distribution in most biopolymers. As their synthesis is controlled by a template direct process in all bio polymers are alike, they all contain the same sequence and numbers of monomers and thus all have the same mass. This p...

Elements of group 13 to 18 of the long form of the periodic table from the P-block elements. In the 'P' block elements, the last electron enters into the 'p' orbital of the outermost shell. 'p' block elements are coming under representative elements along with 's' block elements. They are called so, because they exhibit regular trends in properties with in each group and period. Some general characteristics of 'p' block elements Atomic and ionic radii of 'p' block elements decrease on moving from left to right and increase from top to bottom in any group. Along a period, there is a progressive increase in the nuclear charge of the atoms while the electrons are added to same outer most shell. This causes a decrease in atomic size from left to right along a period. Down a group the effective nuclear charge decreases due to addition of new shells and this results is an increase of atomic size.Ionization enthalpy of 'p' block elements...

Compounds with the same molecular formula but with different structures and so different properties are called isomers and the phenomenon is called isomerism. Different types of isomerism 1) Structural isomerism If the difference in properties result from the difference in the arrangement of atoms within the molecule, it is called structural isomerism. The various types are: a) Ionization Isomerism :- This type of isomerism arises when the compound gives different ions in solution. Eg : [CoBr(NH3)5]SO4 and [CoSO4(NH3)5]Br are ionization isomers. The former gives [CoSO4(NH3)5]2+ and (SO4)2- as ions and latter gives [CoSO4(NH3)5]+ and Br- as ions. b) Co-ordination Isomerism :- Here the cation part and the anion part of the compound are complexed. But the ligands co-ordinated to the metal are different. Eg: [Cu(NH3)4][PtCl4] and [Pt(NH3)4][CuCl4] c) Linkage Isomerism :- If the ligand has two or more different atoms which can act as donor atoms, it can be linked to the metal differently...

Carbon fiber are high performance advanced materials which are stronger than steel, stiffer than titanium and lighter than aluminium. Carbon fibers are generally produced by thermal degradation of materials such as viscose rayon, poly acrylonitrile, pitch, resins, methane, benzene etc. Their properties are influenced by the manufacturing techniques employed. Carbon fibers are generally reinforced in two ways. Carbon fibers reinforced in a light weight matrix such as epoxy resin, polyester resin or polyamide are called carbon fiber reinforced plastics (CFRP). When the carbon fibers are reinforced in a carbon matrix, they are known as carbon fiber reinforced carbons (CFRC).These are otherwise known as carbon-carbon composites. The application of reinforced carbon fibers can be broadly classified into three: 1) High technology sector including, aerospace, military and nuclear fields 2) General engineering sector including sports, transportation and chemical fields 3) Biomedical sector ...

The principle of photography is based on the photochemical reaction of light on certain silver halides. The photographic technique involves the following steps: 1) Preparation of sensitive plate or film :- It is an emulsion of AgBr in gelatin uniformly coated on a glass plate or a celluloid sheet (film) in a dark room.The process is done in dark because AgBr is highly light sensitive. 2) Exposure :- The sensitive plate or film is mounted on a camera and exposed for a few seconds to the image of a properly focused object. An invisible change occurs in that part of the emulsion on which light falls.The chemical reaction is that light reduces AgBr to Ag. Br- + photon -------> electron + Br Ag+ + electron -------> Ag An image of the object is formed on the film which is not visible and therefore called latent image. 3) Development of the latent image :- To make the latent image visible, the film is passed through a reducing bath containing hydroquinone (an organic reducing agent). ...