EVAPORATION AND BOILING (LIQUID TO GAS) On heating particles gain kinetic energy and move faster. In evaporation and boiling the highest kinetic energy molecules can ‘escape’ from the attractive forces of the other liquid particles. The particles lose any order and become completely free to form a gas or vapour. Energy is needed to overcome […]
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Chemists are the people who transform the everyday materials around us into amazing things. Some chemists work on cures for cancer while others monitor the ozone protecting us from the sun. Still others discover new materials to make our homes warmer in the winter, or new textiles to be used in the latest fashions. The
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Sodium Carbonate (Na2CO3) Popularly known as washing soda or soda ash, sodium carbonate is a commercially important compound. In earlier days, it was obtained from the ash of plants and from natural deposits in India and Egypt. Manufacture of Sodium Carbonate Raw Materials Sodium chloride – NaCl (brine solution) Ammonia – NH3 Limestone – CaCO3 (for
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What is Carbon monoxide?. Carbon monoxide is an odourless, tasteless and colourless gas, which is insoluble in water. It is extremely poisonous. Under no circumstances must the gas be inhaled or smelled. It is not usually prepared in a school laboratory. If need be, the gas should be prepared in a fume chamber. Preparation of
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The combustion of carbon: Carbon reacts with oxygen to form two oxides, carbon dioxide, CO2, and carbon monoxide CO. The proportions of these two oxides formed during combustion depend on the conditions. At about 500 ºC, carbon dioxide is produced almost exclusively, provided that oxygen is in excess: C(s) + O2(g) CO2(g) At higher temperatures,
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Apart from diamond and graphite, which are crystalline forms of carbon, all other forms of carbon are amorphous allotropes of carbon. Coke Coke is the amorphous allotrope of carbon, which is derived from coal. When coal undergoes destructive distillation, it yields two allotropes of carbon, namely coke and gas carbon. Destructive distillation is a chemical
What is graphite? Unlike the tetrahedral arrangement of atoms in diamond, the carbon atoms in graphite are arranged in the form of hexagonal rings in layers (Fig.10.2). Each carbon is bonded to only three other carbon atoms in that layer. Different layers of graphite are held together by rather weak forces. Hence they can slide
What is diamond? Diamond is the purest form of natural carbon. It occurs as small crystals embedded in rocks. These are supposed to have been formed by the crystallization of carbon under extreme pressure and temperature in the interior of the earth. Nowadays, synthetic industrial diamonds are being manufactured by subjecting graphite to very high
Cathode reactions (reduction) (-) negative cathode where reduction of the attracted positive cations is by electron gain (reduction) to form metal atoms or hydrogen [from Mn+ or H+, n = numerical charge]. The electrons come from the positive anode. Hydrogen ions are reduced to hydrogen gas molecules. Electrolysis of many dilute salts or acid solutions
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Electroplating is a process of depositing a thin layer of a fine and superior metal (like chromium, zinc, nickel, gold etc.) over the article of a baser and cheaper metal (like iron, copper, brass), with the help of electric current. Uses Electroplating is very useful because of the following reasons: Surface protection e.g. nickel
However, if the compound is unable to ionise it does not conduct electricity it is called a non-electrolyte. In general, the extent to which an electrolyte can break up into ions categorises an electrolyte. This gives a measure of the degree of dissociation (a) of an electrolyte. Based on this degree the electrolytes can be
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In any chemical reaction, the existing chemical bonds are broken and new chemical bonds are formed. Hence, all chemical reactions are fundamentally electrical in nature since electrons are involved in some way or the other in all types of chemical bonding. Many chemical reactions utilize electrical energy, whereas others can be used to produce electrical
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General Preparation of Salts Salts are generally ionic compounds formed by the reaction of an acid with a base. The preparation of these salts involves the treating of different metals and non-metals and their compounds with various acids, bases etc. However, some of them can be prepared by direct combination of the concerned elements or
Bonding in metals Metal atoms have relatively few electrons in their outer shells. When they are packed together, each metal atom loses its outer electrons into a ‘sea’ of free electrons (or mobile electrons). Having lost electrons, the atoms are no longer electrically neutral. They become positive ions because they have lost electrons but the
Van Der Waals Forces Intermolecular attractions are attractions between one molecule and a neighbouring molecule. The forces of attraction which hold an individual molecule together (for example, the covalent bonds) are known as intramolecular attractions. All molecules experience intermolecular attractions, although in some cases those attractions are very weak. Even in a gas like hydrogen,
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Silicon dioxide Has a high melting point – varying depending on what the particular structure is (remember that the structure given is only one of three possible structures), but around 1700°C. Very strong silicon-oxygen covalent bonds have to be broken throughout the structure before melting occurs. Is hard. This is due to the need to
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Graphite Has a high melting point, similar to that of diamond. In order to melt graphite, it isn’t enough to loosen one sheet from another. You have to break the covalent bonding throughout the whole structure. Has a soft, slippery feel, and is used in pencils and as a dry lubricant for things like locks.
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Diamond Has a very high melting point (almost 4000°C). Very strong carbon-carbon covalent bonds have to be broken throughout the structure before melting occurs. Is very hard. This is again due to the need to break very strong covalent bonds operating in 3-dimensions. Doesn’t conduct electricity. All the electrons are held tightly between the atoms,
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As well as achieving noble gas structures by transferring electrons from one atom to another as in ionic bonding, it is also possible for atoms to reach these stable structures by sharing electrons to give covalent bonds. Depending on the number of electron pairs shared between atoms which participate in bonding, covalent bonds are classified
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Ionic (Electrovalent) Bonding Noble gases like neon or argon have eight electrons in their outer shells (or two in the case of helium). These noble gas structures are thought of as being in some way a “desirable” thing for an atom to have. When other atoms react, they try to organize electrons such that their
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