What are the three types of transmission modes?

Based on the direction of data from sender to receiver, there can be 3 types of transmission modes which are discussed below.

What are the disadvantages of E-commerce?

Despite of the many advantages of E-commerce, there are some disadvantages of E-commerce. These disadvantages are minor and most of them will be no more with time and updates in technology. However, following are some of the disadvantages of E-commerce.

What are the three criteria necessary for an effective and efficient network?

A network must meet a certain number of criteria to become useable in real world situation. Most important of these criteria are the three criteria as follows.

What are the fundamental characteristics for the effectiveness of a data communications system?

The effectiveness of a data communications system depends on the following four fundamental characteristics.

What are the five components of a data communications system?

Data Communications: 

Data communications are the exchange of data between two devices using one or multiple forms of transmission medium. The devices are in need to be a part of a communication system made up of hardware and software.

Following are the five components of a data communications system.

Define molarity, molality, normality, mole-fraction.

Molarity (M): 

Molarity is defined as the number of moles of solute per litter of solution. That is,

     W = weight of solute.
     M = molecular mass of solute
     V = volume of solution

Show that the half-life of a second order reaction is inversely proportional to its initial concentration.

For the simple second order reaction 2A→product, we know the rate constant is given by,

For half life,  and 


as k is a constant,

Derive an expression for the rate constant of 2nd reaction of the type, 2A→product.

2A → Product
initial concentration : a molL-1                       →                              0
final concentration (t=t) : (a-x) molL-1             →                  x molL-1


Derive an expression for the rate constant of a first order reaction. Give its units.

Let us consider a first order reaction,

A → product

Suppose at the beginning of the reaction, that is, when t=0, the concentration of A is amolL and when t=t, the concentration of A is (a-x)molL.

For a first order reaction, the rate of reaction,

where k is the rate constant.


Here, c is the constant of integration.

Define order and molecularity.


Order of a reaction is defined by the number of atoms or molecules, whose concentration change during the reaction and determine the rate of the reaction.

For example,

It is a first order reaction.

It is a second order reaction.