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(1) Chemistry does not play a major role in:
A. Explaining superconductivity
B. Design and synthesis new materials having specific magnetic, electric and optical
properties.
C. Explaining ozone depletion.
D. Large scale production of a variety of fertilizers.
Answer - A
Explanation - Chemistry does not deal with explaining superconductivity.
*In superconducting materials the characteristics 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, even though principles involved in Chemistry & Physics go hand to hand.
(2) Matter can be classified at the macroscopic or bulk level as:
A. Elements and molecules
B. Atoms and molecules
C. Solids and liquids
D. mixtures or pure substances
Answer - D
Explanation - At the macroscopic level, the matter is classified as a 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 a fixed composition. The constituents of
pure substances can not be separated by simple physical methods.
(3) In a homogeneous mixture, the components are:
A. do not mix with each other and its composition is not uniform throughout.
B. completely mix with each other and its composition is not uniform throughout.
C. do not mix with each other and its composition is uniform throughout.
D. completely mixed with each other and its composition is uniform throughout.
Answer - D
Explanation - In a homogeneous mixture,
the components are mixed together completely.
has a uniform composition throughout.
(4) Which of the following statements about pure substances is correct?
A. Pure substances are elements only.
B. Pure substances do not have fixed composition.
C. Pure substances have fixed composition.
D. Pure substances are compounds only
Answer - C
Explanation - Pure substances have a fixed composition. These may be both (i.e. either
elements or compounds). The law of constant composition holds good for such substances.
(5) Particles of compounds are:
A. atoms
B. molecules of two or more atoms of different elements
C. homogeneous mixtures
D. heterogeneous mixtures
Answer - B
Explanation - Compounds are made when atoms of two or more different elements combine
together in a fixed ratio to form molecules (viz. water, ammonia, carbon dioxide, glucose, etc.
). Thus the particles of the compound consist of molecules.
(6) Fill up the blanks with a suitable word in the statement, " Physical properties are
those properties which are measured or observed ________ changing the identity or
the composition of the substance ."
A. by
B. with
C. without
D. After
Answer - C
Explanation - 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.
(7) SI units for Base Physical Quantities of length, mass, and current are:
A. meter, gram, ampere
B. meter, kilogram, candela
C. decimetre, kilogram, ampere
D. meter, kilogram, ampere
Answer - D
Explanation - The International System of Units ( abbreviated as SI ) is a modern form of the
metric system and is the most widely used form of measurements.
It comprises 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" symbolized respectively as m, kg, A.
(8) SI unit of density is:
A. kg-1m3
B. kg m-3
C. kg m-2
D. kg m3
Answer - B
Explanation - Since density = mass / volume and SI unit of mass is kg and that of the volume
is m3
∴ using these SI units the unit of density is derived through dimensional analysis:
density = mass / volume
= kg / m3
or, = kg m-3
(9) The Kelvin scale is related to celsius scale as:
A. K = °C + 100
B. K = °C + 32
C. K = °C + 212
D. K = °C + 273.15
Answer - D
Explanation - The relation between the Kelvin scale & Celsius scale of temperatures is -
K = °C + 273.15
Such a relationship is based upon the experimental findings and subsequent conclusion of
Charle's law.
The Kelvin scale is also termed as an "absolute scale of temperature."
It is interesting to note that temperature below 0oC ( ie. negative values ) is possible in the
Celcius scale but in Kelvin scale, the negative temperature is not possible.
(10) In scientific notation for numbers, any number can be represented in the form, N ×
10n where,
A. n is an exponent having positive or negative values and N can vary from 0 to 1.
B. n is an exponent having positive or negative values. N represents a number that can
vary from 1 to 10, but not 10 itself.
C. n is an exponent having positive values only and N can vary from 1 to 10.
D. n is an exponent having positive or negative values and N can vary from 10 to 100.
Answer - B
Explanation - 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 × 10n, where n is an exponent having positive or negative values
and N can vary between 1 and 10, but not 10 itself.
(11) Precision and Accuracy refer to _______ of various measurements for the same
quantity repeatedly and agreement of particular value to the _________ of the result,
respectively.
A. closeness , other values
B. closeness, the true value
C. minimum , true value
D. maximum , true value
Answer - B
Explanation - Precision means the closeness of all the data values measured while accuracy
means the closeness of a particular value with the real value.
For example,
when the reported values are 2.01, and 1.99 gas the result and its true value is 2.00 g.
These values are both precise and accurate.
(12) Significant figures are:
A. first three digits after the decimal point
B. digits before the decimal point
C. digits after the decimal point
D. meaningful digits which are known with certainty
Answer - D
Explanation - Significant digits are certain digits that have significance or meaning to certain
digits in a number. Such digits help scientists to use them with more precise information
about measurement and other numeric data. These digits also help them in rounding off a
very large or very small number
(13) According to Gay Lussac’s Law of Gaseous Volumes, " when gases combine or
are produced in a chemical reaction they do so in a ______ ratio by volumes provided
all gases are at the same temperature and pressure."
A. simple
B. equal
C. inverse
D. Uncertain
Answer - A
Explanation - Gay lussac’s law states that when gases combine or are produced in a
chemical reaction they do so in a simple ratio by volume provided all gases are at the same
temperature and pressure.
Mathematically, the law is expressed as,
[V/n] = k
where V represents the volume of the gas, n denotes the number of moles of the gas & k is
the proportionality constant.
Thus, the volume ratio must be related to the relative number of molecules.
This relationship was crucial in establishing the formula of simple molecules at a time when a
distinction between atoms and molecules was not clearly understood.
(14) According to Avogadro Law, equal volumes of all gases at the same temperature
and pressure should contain _______ number of molecules.
A. different
B. unequal
C. similar
D. Equal
Answer - D
Explanation - Avogadro's law states that " equal volumes of all gases at the same
temperature and pressure contain an equal number of molecules."
(15) Molecular mass of a compound is the ________ of atomic masses of elements
present in a molecule.
A. average
B. sum
C. maximum
D. Lowest
Answer - B
Explanation - Molecular mass is the sum of atomic masses of the elements present in a
molecule.
For example ; Molecular mass of CO2 = Σ atomic mass of one carbon atom & atomic mass
of two oxygen atoms
= [ 12 + 2(16) ]u
= 44u.
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