Test: Importance & Scope Of Chemistry

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The prefix used for 10-18 is:


The prefix used for 10-18 is atto-

Additional Information:metric prefix is a unit prefix that precedes a basic unit of measure to indicate a multiple or submultiple of the unit. Each prefix has a unique symbol that is prepended to any unit symbol. Some important prefixes are given below: 

What is a prefix ? Give some common prefixes for multiples and submultiples  - CBSE Class 11 Physics - Learn CBSE Forum


One atomic mass unit (amu) is closest to:​

  • An atomic mass unit (symbolized AMU or amu) is defined as precisely 1/12 the mass of an atom of carbon-12.
  • 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.
  • 1 AMU = 1.67377 x 10 -27 kilogram or 1.67377 x 10 -24 gram.

The number of base SI units is:


The standard units of measurement defined by the ISU for the seven base quantities are SI base units All other SI units are derived from it.

Additional Information: 7 Basic SI units with their quantities are: 



The SI unit of time is:


The S.I. unit of time is second(s).
Additional Information: A second can be defined as  1/86400th part of a mean solar day,  i.e., =1/86400 × one mean solar day.


The two effective drugs which act as life-saving drugs for cancer therapy and AIDS victims respectively are:

  • Cisplatin is particularly effective against testicular cancer.
  • Taxol (paclitaxel) is a mitotic inhibitor used in cancer chemotherapy.
  • AZT is used for helping AIDS victims.

Additional Information: Its mode of action has been linked to its ability to crosslink with the purine bases on the DNA; interfering with DNA repair mechanisms, causing DNA damage, and subsequently inducing apoptosis in cancer cells. 


Which of the following statements is/are correct?

  • A molecule is made up of atoms bonded together. 
  • The law of definite proportions, sometimes called Proust's law, or the law of constant composition states that a given chemical compound always contains its component elements in a fixed ratio (by mass) and does not depend on its source and method of preparation.

Since both statements A and B are correct, the correct option is D. 


The coefficient in 6.65 × 104 is:


Here, 6.65 is the coefficient and 10is the exponent.

Explanation: A coefficient is a number or an alphabet that is multiplied by a variable of a single term or the terms of a polynomial. For example, in the term 7x, 7 is the coefficient. 


The ‘Candela’ is the unit of:

  • Luminous intensity is a measure of the wavelength-weighted power emitted by a light source in a particular direction per unit solid angle.
  • The SI unit of luminous intensity is the candela, an SI base unit.

The number of significant figures in 3256 is:

  • The significant figures of numbers are digits to convey the meaning that contributes to its measurement resolution.
  • Non-zero digits are always significant.
  • Here, 3256, this number has four non-zero numbers.
  • That's why it has four significant figures.

The SI unit of electric current is:

  • Electric current is defined as the rate of flow of charge
  • Since the charge is measured in coulombs and time in seconds, the electric current unit is Coulomb/Sec ( C/s )
  • Where, coulomb/sec is defined as Ampere

So the Ampere is the SI unit of the current.


A number of significant figures in 0.001520 is:

  • The significant figures of numbers are digits to convey the meaning that contributes to its measurement resolution.
  • Non-zero digits are always significant.
  • Here, the number of Significant figures in 0.001520 is 4.

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:​

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

The unit of amount of substance is:

  • The mole, denoted by the symbol mol, is the SI unit of the amount of substance.
  • One mole contains exactly 6.022 140 76 x 1023 elementary entities.
  • This number is the fixed numerical value of the Avogadro constant, NA, when expressed in the unit mol–1 and is known as the Avogadro number.
  • The value of Avogadro’s number is fixed and the value is NA = 6.022 x 1023.

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

  • The significant figures of numbers are digits to convey the meaning that contributes to its measurement resolution.
  • Non-zero digits are always significant.
  • 6.26 & 0.00267 contains 3 significant figures while 5.8 has two significant figures and 0.03 contains least that is 1.

Therefore, the correct answer is 0.03


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:​

  • Precision indicates how closely repeated measurements match each other.
  • Accuracy indicates how closely a measurement matches the correct or expected value.

Since the readings closely match the result and the expected value, the correct answer is that the values are both accurate and precise. 


The number of significant figures in 3.1205 are:


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


The scientific notation for 0.00016 is:​


Move the decimal point to the right of 0.00016 up to 4  places.

The decimal point was moved 7 places to the right to form the number 1.6

Since the numbers are less than 10 and the decimal is moved to the right, so we use a negative exponent here.

⇒ 0.00016 = 1.6 × 10-4


  • Scientific notation is a form of presenting very large numbers or very small numbers in a simpler form.
  • Scientific notation is used to represent the numbers that are very huge or very tiny in a form of multiplication of a single-digit number and 10 raised to the power of the respective exponent.
  • The exponent is positive if the number is very large and it is negative if the number is very small. 

Suppose the elements X and Y combine to form two compounds XY2 and X3Y2. When 0.1 mole of XY2 weighs 10 g and 0.05 mole of X3Y2 weighs 9 g, the atomic weights of X and Y are:


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


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


The correct option is B


In 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.


Molecular mass of glucose molecule (C6H12O6) is:


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.

The molecular formula of glucose is C6H12O6

  • The atomic mass of H = 1
  • The atomic mass of C = 12
  • The atomic mass of O = 16

Molecular mass of C6H12O6 = 12 (Atomic mass of Hydrogen) + 6(Atomic mass of carbon) + 6(Atomic mass of oxygen)

= 12 × 1 + 6 × 12 + 6 × 16

= 12 + 72 + 96 = 180 u.

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