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QUESTION: 1

What will be the molality of the solution containing 18.25 g of HCl gas in 500 g of water?

Solution:

Given:

Mass of HCl = 18.25 gm

Molar mass of HCl = 36.5 g/mol

Mass of water = 500 gm

= 0.5 kg

No. of moles of HCl;

= (Mass of HCL)/(Molecular mass of HCL)

=18.25/36.5 = 0.5 mol

Molality is,

= (No. of Moles/ Mass of Solvent) = 0.5/0.5

So

Molality of solution is 1 m.

QUESTION: 2

The use of alkali in aqueous solution leads to which type of hydrolytic reaction?

Solution:

The use of alkali in aqueous solution leads naturally to another type of hydrolytic reaction, namely, alkali fusion, wherein the proportion of alkali is greatly increased and that of water correspondingly reduced.

QUESTION: 3

The prefix used for 10^{-18} is:

Solution:

The prefix used for 10^{-18} is: atto

QUESTION: 4

The coefficient in 6.65 x 10^{4} is:

Solution:

Here 6.65 is the coefficient and 10^{4 }is the exponent.

QUESTION: 5

One atomic mass unit (amu) is closest to:

Solution:

One atomic mass unit is defined as 1/12 the mass of a carbon-12 atom. The carbon-12 (C-12) atom has six protons and six neutrons in its nucleus. In imprecise terms, one AMU is the average of the proton rest mass and the neutron rest mass. This is approximately 1.67377 x 10^{-27} kilogram (kg), or 1.67377 x 10^{-24} gram (g).

QUESTION: 6

The number of base SI units is:

Solution:

Base is system means fundamental physical quantities and there are 9 fundamental physical quantities but only 7 have units so number of base SI units is 7.

QUESTION: 7

The SI unit of time is:

Solution:

The SI unit of time, the second, symbols, is easy enough to define, but time itself can only be defined in reference to other quantities.

QUESTION: 8

The ‘Candela’ is the unit of:

Solution:

Luminous intensity is a measure of the wavelength-weighted power emitted by a light source in a particular direction per unit solid angle, based on the luminosity function, a standardized model of the sensitivity of the human eye. The SI unit of luminous intensity is the candela , an SI base unit.

QUESTION: 9

The number of significant figures in 3256 is:

Solution:

3256, This number has four non zero numbers . That's why it has four significant figures.

QUESTION: 10

The SI unit of electric current is:

Solution:

The SI unit for measuring an electric current is the ampere, which is the flow of electric charge across a surface at the rate of one coulomb per second. Electric current is measured using a device called an ammeter.

QUESTION: 11

A number of significant figures in 0.001520 is:

Solution:

All non-zero digits are significant. Zeros before the decimal point are not significant. Zeros to the right of the decimal point are significant.

QUESTION: 12

If the true value for a result is 2.00 g and a student takes 2 measurements and reports the results as 1.95 g and 1.93 g, then we can conclude that:

Solution:

Precision indicates how closely repeated measurements match each other. Since both the values are close to each other, they are precise and since their is a difference between the mean value and true value, they are not accurate.

QUESTION: 13

The unit of amount of substance is:

Solution:

Amount of Substance is also called as material quantity. The amount of substance refers to a standards-defined quantity that measures the size of an ensemble of elementary entities, such as atoms, molecules, electrons, and other particles. Amount of substance appears in thermodynamic relations such as the ideal gas law, and in stoichiometric relations between reacting molecules as in the law of multiple proportions. The unit symbol of amount of substance is mole.

QUESTION: 14

Out of the numbers: 6.26, 5.8, 0.00267, 0.03, the one with the least significant figures is:

Solution:

6.26 & 0.00267 contains 3 significant figures while 5.8 has two significant figures and 0.03 contains least that is 1.

QUESTION: 15

If the true value for a result is 3.00 m and a student records two readings as 3.01 m and 2.99 m, then we can conclude that:

Solution:

Precision indicates how closely repeated measurements match each other.

Accuracy indicates how closely a measurement matches the correct or expected value.

QUESTION: 16

The number of significant figures in 3.1205 are

Solution:

The answer is 5 because all non zero digits and zero between the non zero digits are significant.

QUESTION: 17

The scientific notation for 0.00016 is:

Solution:

Here, the decimal has to be moved four places to the right side and hence -4 is the exponent in the scientific notation.

QUESTION: 18

Suppose the elements X and Y combine to form two compounds XY_{2} and X_{3}Y_{2}. When 0.1 mole of XY_{2} weighs 10 g and 0.05 mole of X_{3}Y_{2} weighs 9 g, the atomic weights of X and Y are

Solution:

Let atomic weight of element X is x and that of element Y is y

QUESTION: 19

If we add the numbers 6.68 and 0.8, the result will be:

Solution:

During addition, the result cannot have more digits to the right of the decimal point than either of the original numbers. Since there is only 1 digit after the decimal point in 0.8 so the result 7.48 should be rounded off to 1 decimal point i.e. 7.5.

QUESTION: 20

Molecular mass of glucose molecule (C_{6}H_{12}O_{6}) is:

Solution:

Molecular mass : The sum of the atomic masses of all the atoms in a molecule of a substance is called the molecular mass of the molecule.

Generally we use relative atomic masses of atoms for calculating the molecular mass of 1 mole of any molecular or ionic substances.

Molecular formula of glucose is C_{6}H_{12}O_{6}

Atomic mass of H = 1

Atomic mass pf C = 12

Atomic mass of O = 16

Molecular mass of C_{6}H_{12}O_{6} = 12(Atomic mass of Hydrogen) + 6(Atomic mass of carbon) + 6(Atomic mass of oxygen)

= 12 x 1 + 6X12 + 6X16

= 12 + 72 + 96 = 180 u.

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