what is error and its different types (in chemistry)

Q.1. What is ERROR ?

Error is defined as the numerical difference between measured value and true value in analytical determination.

Q.2. What are the different types of 

         error ?

Error is of two types :-
           1. Determinate error
           2. Indeterminate error.

1. Determinate error

The errors which can be avoided or whose magnitude can be determine and can be rectified are called determinate error.
These errors are caused by defecting experiment apparatus or technique when in the measurement of weight of substance is uncalibrated weight are used then the weight in term of error is known as determinate error.

Uses -

This error can be rectified or remove replacing uncalibrated weight.

Determinate error is of  three types 

1. Instrumental error.
2. Personal error.
3. Error of method.

1. Instrumental error

This type of error arises due to the faulty construction of chemical balance, use of uncalibrated weight, uncalibrated glassware or other instrument attack of reagent on glassware. These are known as instrumental error.
This type of error can be removed by using calibrated apparatus and appropriate correction applied to the accurate measurement.

2. Personal error

this error are due to faults in individual analysis and not connected with the apparatus aur procedure.
Example :
(a) in the mechanical loss of substance during various steps of analysis.
(b) if a solution is transferred from one container to another container then loss of 1 -2 drops solution.
(c) under washing and overdrying precipitate.
(d) insufficient pulling before weight.
(e) incorrect reading of the end point During titration. These are personal error.
This error can be removed by experiment and carefulness.

3. Error of method

In the analysis some error occur due to the wrong procedure by which many chemical reaction maybe incomplete or site reaction may take place.
This error can be rectified or removed by using proper method.
Example : incorrect sampling, incompleteness reaction, unsatisfactory solubility of precipitate, co-precipitate, decomposition volatilization etc.

2. Indeterminate errors 

applying similar condition and method in the chemical analysis their arises some error in the experimental value which are beyond control of analysis are known as indeterminate error.
This error cannot be rectified or removed but can minimise by taking proper observation.
Example : rise and fall of temperature, change of atmospheric vapour pressure, presence of impurities in air, insufficient light in the laboratories, lack of concentration in the analysis.
   

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