Some Basic Concepts of Chemistry - Online Test

Q1. Chemistry does not play a major role in
Answer : Option C
Explaination / Solution:

Chemistry does not deal in explaining superconductivity.

*In superconducting materials the charecteristics of superconductivity appear when the temperature is lowered below a critical temperature.

*The onset of superconductivity is accompanied  by abrupt changes in physical properties which are more related to phase transitions of the material .

These aspects of  studies in properties of materials  are better related to studies in the fields of Physics , eventhough  principles involved in Chemistry & Physics go hand to hand. 


Q2. Matter can be classified at the macroscopic or bulk level as


Answer : Option C
Explaination / Solution:

At macroscopic level matter is classified as mixture or pure substances .A mixture contains two or more components (in any ratio ) present in it , for example -- sugar solutions in water , tea , air , alloys like brass ,bronze etc. Pure substances (viz. copper , silver , gold , water , glucose etc . ) have fixed composition . The constituents of pure substances can not be separated by simple physical methods.

Q3. In a homogeneous mixture,the components are


Answer : Option D
Explaination / Solution:

In a homogeneous mixture , (i) the components are mixed together completely , (ii) has a uniform composition throughout.

Q4. Which of the following statements about pure substances is correct ?


Answer : Option B
Explaination / Solution:

Pure substances have fixed composition..These may be both (ie. either elements or compounds ) . The law of constant composition holds good for such substances .

Q5. Particles of compounds are


Answer : Option C
Explaination / Solution:

Compounds are made when, atoms of two or more different elements combine together in fixed ratio to form molecules .(viz. water , ammonia , carbon- di- oxide glucose etc. ) . Thus the particles of compound consists of molecules.

Q6. Fill up the blank with suitable word in the statement, " Physical properties are those properties which are measured or observed--------------- changing the identity or the composition of the substance ."


Answer : Option D
Explaination / Solution:

A substance is identified by its composition , hence for measuring physical properties of a substance its identity must be retained , (or should not be changed ) Hence , the given statement , " Physical properties are those properties which are measured or observed without changing the identity or composition of the substance." is correct.

Q7. SI units for Base Physical Quantities of length, mass and current are


Answer : Option D
Explaination / Solution:

The International System of units ( abbreviated as SI ) is modern form of metric system , and is most widely used form of measurements . It comprises of a coherent system of measurement built of seven base units . The base units for length , mass and current in this system of measurements are , " meter , kilogram , ampere " ,symbolised respectively as as m ,kg , A

Q8. The kelvin scale is related to celsius scale as :


Answer : Option A
Explaination / Solution:

The relation between Kelvin scale & Celcius scale of temperatures is - K = °C + 273.15 Such a relation is based upon the experimental findings and subsequent conclusion of Charle's law . The Kelvin scale is also termed as " absolute scale of temperature." It is interesting to note that temperature below 0o C ( ie. negative values ) are possible in Celcius scale but in Kelvin scale , negative temperature is not possible .

Q9. Precision and Accuracy refer to _______ of various measurements for the same quantity repeatedly and agreement of a particular value to the ------- -------- of the result , respectively.


Answer : Option A
Explaination / Solution:

Precision means closeness of all the data values measured while accuracy means closeness of particular value with the real value. For example , when the reported values are 2.01, and 1.99 g as the result and its truevalue is 2.00 g . These values are both precise and accurate.

Q10.

In scientific notation for numbers, any number can be represented in the form ,

N × 10  where,

Answer : Option D
Explaination / Solution:

Scientific notation is conveniently used to  represent  extremely large or even very small  numerical values . It is an exponential notation in which any number can be represented in the form ,  N x 10n , where  n is an exponent having positive or negative values and N can vary between  1 and  10  , but not  10 itself.