Hack tech fact

Start menu                            Commands:>  > My Documents Used to open my Documents folder, where you can access /store /manipulate your letters, reports, documents and other documents.  > My music Open music folder, where you can store music files and other audio files. > My pictures Open my picture folder, where you can store digital photos, images and graphic files.  > My computer  Gives access and information about all the storage Disks, SSD, Hardware and other devices connected to your system.  > Control panel Provide options to customize the appearance and functionality of your system add or remove programs, setup network connection, setup user account, setup printer and other hardware. > Set program Access and Defaults Used to allow the user to interact with the default programs and applications like web Browsing and desktop application. > Connect to Used to connect to the internet. > Printers and faxes Used to show installed Printers and faxes

Packages It is an application program that is designed to handle a particular task. It can be either a routine package or designed for a specific purpose. All input/output transfers and error situation are aromatically handled by the package itself.   Example of packages DTP :  It stands for Desk Top publishing, which allows many organization's to produce camara ready artwork in hour, thereby saving considerable expenses on outside expertise. There are some special types of word processing packages, which can fulfill the requirements of publishing industry and hence these came to know as Desk top publishing packages. The most common DTP in use in india are Page maker and ventura for English language and for indian language shreelipi, indica etc. DBMS : It is the Database Management system that allows the user to setup, maintain and manipulate a database management task may include controlling excel to the database, extracting data selectively from different parts of database, finan

Classification of     digital computer -> Digital computer has been classified into two types: 1- Purposes-wise  2- Size-wise  Purposes-wise   1- special purpose : used to perform specific task. The program or institutions set in permanently stored in such a machine, which perform a single task quickly and effectively can be used for separate purposes like weather forecasting etc. 2- Genaral purpose : used for different purposes. Numerous appreciation are loaded to different purposes that can be used for office Automation, Research, Entertainment, Commercially purposes, Education etc.  Size-wise 1- micro Computer : Lot of changes has taken place in microprocessor architecture in these days. The introduction of multimedia, 3D animation, editing, gaming etc,  technology into a a processor for entertainment media is very popular now days. The present range of CPU included -.  Intel xeon E5205, Intel i7-975 Extreme Edition Bloomfleld, AMD Athlon II 240 Regor, Intel Core 2 duo T9400 etc.

Units of computer-> A computer system is made up mainly three Units.  1- Input unit 2- system unit or processing unit 3- Output unit Input unit ->   This unit, which is used in transferring the data or instructions to the computer system, is called as the input unit. Also the input unit is a collection of input devices. Examples of input devices available in input unit are keyboard, mouse and microphone etc. System unit or processing unit->    A system unit mainly consists of the followings:  1- Central processing unit (CPU) or microprocessor.  2- memory unit with primary memory and secondary memory drives.  3- SMPS (Switch mode power supply)  4- Motherboard or pcb (Printed circuit Board).  5- Drive controller card. 6- Math Co- processor. 7- Ports. 8- Adaptor.   Central processing unit (CPU) -> The central processing unit is regarded as the brain of the computer. The CPU provides the fundamental command and instruction environment for the computer .     The major units of C

Features of                                computers- Computer has become the life style of mankind because of the following characteristics:  a >  Speed: The processing speed of a computer is very fast/very high. It can perform any type of calculation within a fraction of seconds. The speed of the computer can be measured in pico seconds i.e. Billionth (10-¹²) part of a second. b> Accuracy: The output of result given by the computer is very accurate. A calculator can give maximum 9 to 10 digitise results wheather decimal digit may cross the range where as a computer can give the accurate decimal values. A computer never gives any wrong information unless and until the user does because computer does all the operation using electronic circuits. c> Storage: One of the most important characteristics is that a computer can store large amount of data and whenever it is required to retrieve it can be very easily. d> versatility: A computer can perform varieties of tasks. The pro

Are the molecularity and reaction order different for elementary reactions?    It may be stated once again that the total number of molecules or atoms which participate in a reaction as represented by the chemical equations is known as the molecularity of the reaction. The sum of the power to which the concentrations are raised in the rate law is termed as the order of a reaction. Let us consider an elementary reaction of the type.        2A + B --> Products.          Since the rate of a reactio n is proportional to number of collisions between the atoms or molecules of the reactants, and the number of collisions is proportional to the concentration of each reactant species, the rate of the above reaction                alfa [A²] [B²].          rate = k [A²] [B]  Molecularity of reaction =       2 + 1 = 3    It shows that the molecularity and order of an elementary reaction are the same.

Molecularity of a reaction:   It may be defined as the number of reacting species (atoms, ions or molecules) that collide simultaneously to form the product in the rate determining step of a chemical reaction.       Now, we have two types of chemical reaction, namely: (1) Elementary reactions, android (2) Complex reactions.

Difference between rate of reaction and rate constant:   1- Rate of reaction (r) = Rate constant (k)×(conc), when concentration is one molar, r = k. 2- Rate of reaction depends on the concentrations of reactants and the temperature whereas the rate constant does not depend on the temperature. 3- The rate of reaction at a particular instant is the instantaneous rate of change of concentration of any one of reactant or product at that instant. On the other hand the rate constant is a constant of proportionality, and it equals the rate of reaction when the molar concentration of the reactants is unity.

Units of rate:  We have the rate of reaction= Change in concentration of the reaction or product _____________________________               Time taken   Thus,  reaction rate has the units of concentration divided by time. Concentration in moles per litre (molar concentration, M =mol dm-³), and time may be in seconds, (s), minutes (min), hours (h), days (d) or possibly years (y).  Therefore, the units of reaction rates may be        mol dm-³ s-¹ or mols/ liter, sec or Ms-¹  mol dm-³ min-³ or moles/liter min, or M min-¹  mol dm-³h-¹ or moles/ liter- hour or Mh-¹ and so on  In gaseous reaction, pressure is normally used and thus rate is expressed in atm sec-¹ or atm mim-¹.

 Variation of reactant concentration with time:     As stated above, the rate of a reaction is measured by the rate of decrease in concentration of a reactant or the rate of increase in concentration of product with time. Thus, the rate at which the concentration of reacting substance changes with time is known as rate of reaction of velocity of reaction. This means that the concentration of a reactant decreases with time. Let us study now at what rate the concentration varies. Decomposition of N²O⁵ in gaseous phase or its solution in CCl⁴ takes place at a convenient rate as a in        2N²O⁵ --> 4NO² + O² 

 Modified collision theory:  Since the collision theory fails in a number of cases giving the rate of reaction values of various gaseous reaction, it is concluded that collisions between molecules cannot be the only factor, required in determining the rate of a reaction. So, Arrhenius modified the simple collision theory. According to this modified theory.  (I) The collisions between all molecules cause chemical reaction. (II) The collisions between the molecules which possess energy of activation cause the chemical reaction. It means that if the energy of the colliding molecules is less than the energy of activation, no reaction take place. If the energy is equal to or greater than energy of activation, reaction occurs Thus, eqn (iv), k=ze -Ea/RT  is modified, to account for the deviations from the collision theory, in the form k=pZ e -Ea/RT             Where p is the probability factor which is a measure of an increase or decrease of the speed of reactions. The value of p varies from

 Collision theory of unimolecular reactions:  This theory was proposed independently by max trautz in 1916 and William Lewis in 1918. This theory qualitatively explain how chemical reactions occur and why reaction rates differ for different reaction. According to this theory, the reacting molecules must collide to react as a result of which the chemical reaction occurs. But, in fact, not all collisions are effective. Only a certain percentage of total number of collisions produce any significant chemical reaction. In other words, successful (i.e., effective) collisions give rise to chemical reaction. It is just like that a few number of crackers burst with sound and hence effective while others are ineffective producing no sound. The effective collisions between the reacting molecules causing any chemical change depends on two conditions (e.g., postulates) :   (I) the colliding molecules must have enough energy, known as activation energy to cause a reaction, and. (II) the reacting mol

Effect of      temperature     reaction rate:     As discussed in sec 4.1.6, the rates of chemical reactions increase with increase in temperature. The rate constant becomes almost doubled for a rise in temperature of 10°C, so the ratio of rate constants of reaction at two different temperature differing by 10°C is termed as temperature coefficient, i.e,                                               Temperature coefficient =               k ( t+10 )               ------------- is 2 to 3.                   Kt         This shows that as an approximate rule, the rate constant becomes double for a rise in temperature of 10°C.

 Reaction of high molecularity are rare:   As discussed in the preceding section, the rate of a reaction is proportional to the number of collisions between the reactants molecules. With the increase in number of reactant molecules the chances of collisions between the molecules become less. It means that the number of collisions between 3 reacting molecules becomes less than that between two molecules. Thus, when a reaction involves more than 3 molecules the number of collisions decreases and hence the probability of the occurrence of the reaction become less. It is, therefore, the reaction of higher molecularity, i.e., greater than 3 are rare. In such cases, complex reaction occuring in various steps involving one, or two or at the best 3 molecules are considered.