Facebook Twitter Instagram
    ScienceMotive
    • Class 9
      • Matter in Our Surroundings
      • Is Matter Around Us Pure
      • Atoms and Molecules
      • Structure of the Atom
      • The Fundamental Unit of Life
    • Class 10
      • Chemistry
    • Class 11
      • Chemisrty
        • Chapter – 1 Some Basic Concepts of Chemistry
        • Chapter – 2 Structure Of Atom
        • Chapter – 3 Classification of Elements and Periodicity in Properties
        • Chapter – 4 Chemical Bonding and Molecular Structure
        • Chapter – 5 States of Matter
        • Chapter – 6 Thermodynamics
        • Chapter – 7 Equilibrium
        • Chapter – 8 Redox Reaction
        • Chapter – 10 s-Block Elements
        • Chapter – 13 Hydrocarbons
    • Class 12
      • Chemistry
        • The Solid State
        • Solutions
        • Electrochemistry
        • Chemical Kinetics
        • Surface Chemistry
        • p – Block Elements
        • d & f Block Elements
        • Coordination Compounds
        • Haloalkanes and Haloarenes
        • Alcohols, Phenols and Ethers
        • Aldehydes, Ketones and Carboxylic Acids
        • Amines
        • Biomolecules
        • Polymers
        • Chemistry in Everyday Life
    • Practice Questions
      • +1
      • +2
    • Test Series
      • Class 9 Test Series
      • Class 10 Test Series
      • Class 11 Test Series
      • Class 12 Test Series
    • World
      • Current Affairs
      • General Knowledge
    ScienceMotive
    Home » Solved worksheet Some Basic Concepts of Chemistry

    Solved worksheet Some Basic Concepts of Chemistry

    Dr. Vikas JasrotiaBy Dr. Vikas JasrotiaOctober 3, 2020No Comments
    Share
    Facebook WhatsApp Telegram Twitter Email

    Solved worksheet Some Basic Concepts of Chemistry

    Solved worksheet Some Basic Concepts of Chemistry is all about subjective and objective knowledge.

    Q1. How many significant figures are there in (i) 3.070 and (ii) 0.0025?     
    Ans 1. (i) 4                  (ii) 2

    Q 2. How many significant figures are present in the answer of the following calculation:  .0125 + 0.8250 + 0.025
    Ans 2.  0.86

    Q 3. The density of vanadium is 5.96 g cm3. Express this in SI unit.
    Ans3. 5960 kg m3

    Q 4. The body temperature of a normal healthy person is 370C. Calculate its value in 0F.
    Ans 4. We know
    0F = 9/5(0C) + 32
    0F = 9/5(37) + 32
    0F = 9 × 7.4 + 32 = 98.6 0F

    Q5. At what temperature will both the Celsius and Fahrenheit scales read the same value?
    Ans. Let x be the common reading.
    Then, C = F = x
    We knoe the relation between 0C and 0F
    0C=5/9 (0F-32), and substituting x for 0C and 0F, we get
    x =5/9 (x-32)
    x =5/9x – 5/9×32
    x – 5/9x = 5×32/9
    4/9x = – 5×32/9
    x = – 5×32/4 = -40
    So, -40C = -40F
    Hence, at -40 degrees, the readings on the Celsius scale and the Fahrenheit scales are the same.

    Q6. Express the following in the scientific notation: (i) 0.0048 (ii) 234,000
    Ans 6. i). 4.8 × 10-4                 ii) 2.34 × 105

    Q7. Given the numbers: 161 cm, 0.161 cm, O.OI61 cm. Write The number of significant figures for these three numbers.
    Ans 7. 3,3,3

    Q8. Read the following and choose the incorrect statements.
    (i) Both weight and mass are the same quantities used for measurement of the amount of matter present in a substance
    (ii) Mass and weight of a substance vary from one place to another due to a change in gravity.
    (iii) ST unit of mass is kilogram and while the SI unit of weight is the gram.
    (a) (i) and (iii)                                     (b) (ii) and (iii)
    (c) (i) and (ii)                                      (d) All of these
    Ans 8. (d) All of these

    Q9. A student performs a titration with different burettes and finds titre values of 25.2 mL, 25.25 mL, and 25.0 mL the number of significant figures in the average titre value is  
    a) 1                       b) 3 
    c) 2                       d) 4
    Ans 9. (b)  Calculate the average value of different titre values.
    Then use the rule to determine the significant figures for mathematical calculation.
    Average value =  25.2  +  25.25  +  25.0/3  =   75.45/3
    = 25.15  = 25.2 mL  The number of significant figure is 3

    Solved worksheet Some Basic Concepts of Chemistry

    Q10. What will be the answer of 77.32-6.3? 
    a) 71.02                                       b) 71.0           
    c) 71.2                                         d) 71.1
    Ans 10. (b)  The answer is to be reported up to the same number of decimal places as that of the term with the least number of decimal places. This after rounding off 71.02 becomes 71.0.

    Que 11. What is the unit factor method? Express the following in SI units – 93 million miles (distance between earth and sun)
    Ans 11. The method to convert units from one system to another is called the unit factor method.
    93 million miles = 93 × 106 miles
    1 mile = 1.60934 km = 1.60934 × 103 m

    Que 12. What do mean by gram atomic mass. one million silver atoms weigh 1.79 x 1016 g. Calculate the gram atomic mass of silver.
    Ans 12. The atomic mass of an element expressed in grams is the gram atomic mass
    Number of silver atoms = 1 million = 1 × 106
    Mass of one million Ag atoms = 1.79 × 1016g
    Mass of 6.023 x 1023 atoms of Silver = 1.79 × 1016g x 6.023× 1023/1 × 106
    = 107.8 g

    Que 13. Copper oxide obtained by heating copper carbonate or copper nitrate contains copper and oxygen in the same ratio by mass. Which law is illustrated by this observation? State the law.
    Ans 13. Law of Definite Proportions: According to this law a chemical compound
    always consists of the same elements combined together in the same ratio,
    irrespective of the method of preparation or the source from where it is taken.

    Que 14. Write the empirical formula of the following:
    (a) N2O4 (b) C6H12O6 (c) H2O (d) H2O2
    Ans 14. (a) NO2 (b) CH2O (c) H2O (d) HO

    Que 15. Chlorine has two isotopes of atomic mass units 34.97 and 36.97. The relative abundance of the isotopes is 0.755 and 0.245 respectively. Find the average atomic mass of chlorine.
    Ans 15. Average atomic mass = 34.97 × 0.755 + 36.97 × 0.245 = 35.46 u

    Solved worksheet Some Basic Concepts of Chemistry

    Que 16. How are 0.50 mol Na2CO3 and 0.50 M Na2CO3 different?
    Ans 16. Molar mass of Na2CO3 = 2 × 23 +12 + 3 × 16 = 106 g / mol
    0.50 mol Na2CO3 means 0.50 × 106 = 53 g
    0.50 M Na2CO3 means 0.50 mol i.e. 53 g of Na2CO3 are present in I L of the
    solution.

    Solved worksheet Some Basic Concepts of Chemistry is all about subjective and objective knowledge

    Que 17. What is the percentage of carbon, hydrogen, and oxygen in ethanol?
    Ans 17. Molecular formula of ethanol is: C2H5OH
    Molar mass of ethanol is: (212.01 + 61.008 + 16.00) g = 46.068 g
    Mass per cent of carbon = (24.02g / 46.068g) ×100 = 52.14%
    Mass per cent of hydrogen = (6.048g / 46.068g) × 100 = 13.13%
    Mass per cent of oxygen = (16.00 g / 46.068g) ×100 = 34.73%

    Que 18. What do mean by molarity? Calculate the molarity of NaOH in the solution
    prepared by dissolving its 4 g in enough water to form 250 mL of the solution.
    Ans 18. The number of moles of solute dissolved per litre (dm3) of the solution is called molarity.
    Since molarity (M) = No. of moles of solute /Volume of solution in litres
    = (Mass of NaOH / Molar Mass of NaOH) /0.250 L
    = (4 g / 40 g 0.1 mol) / 0.250L = 0.1 mol / 0.250 L
    = 0.4 mol L-1  = 0.4 M

    Que 19. Express the following in the scientific notation with 2 significant figures-
    (a) 0.0048                         (b) 234,000                       (c) 200.0
    Ans 19. (a) 4.8 × 10-3                       (b) 2.3 × 105                      (c) 2.0 × 102

    Que 20. Calculate the number of atoms in each of the following:
    (i) 52 moles of Ar   (ii) 52 u of He         (iii) 52 g of He
    Ans 20. (i) 1 mole of Ar = 6.022 × 1023 atoms of Ar
    52 mol of Ar = 52 × 6.022 × 1023 atoms of Ar
    = 3.131 × 1025 atoms of Ar
    (ii) 1 atom of He = 4 u of He
    Or
    4 u of He = 1 atom of He
    1 u of He = 1/4 atom of He
    52 u of He = 52/4 atom of He
    = 13 atoms of He
    (iii) Molar mass of He = 4 g/mol
    4 g of He contains = 6.022 × 1023 atoms of He
    52 g of He contains = 6.022 × 1023 x 52/4 = 78.286 x 1023 atoms of He

    Que 21. What is the difference between empirical and molecular formulas? A compound contains 4.07 % hydrogen, 24.27 % carbon, and 71.65 % chlorine. Its molar mass is 98.96 g. What are its empirical and molecular formulas?
    Ans 11. An empirical formula represents the simplest whole-number ratio of various atoms present in a compound whereas the molecular formula shows the exact number of different types of atoms present in a molecule of a compound.

    The empirical formula of the above compound is CH2Cl.
    empirical formula mass is 12 + (1 x 2) + 35.5 = 49.5
    n= Molecular Mass / Empirical Formula Mass = 98.96 / 49.5 = 2
    Hence molecular formula is C2H4Cl2

    Solved worksheet Some Basic Concepts of Chemistry

     

    Advertisement
    Solved Worksheet Some Basic Concepts of Chemistry
    Share. Facebook Twitter Pinterest LinkedIn Tumblr Email
    Dr. Vikas Jasrotia
    • Website

    Related Posts

    Write the favourable factors for the formation of ionic bond

    October 17, 2022

    Chemical Bonding Class 11 Questions and Answers PDF

    October 16, 2022

    Chemical Bonding and Molecular Structure – Short Notes

    October 14, 2022

    Leave A Reply Cancel Reply

    READ ALSO

    Carbon and Its Compounds

    January 23, 2023

    An element X (atomic number = 17) reacts with an element Y (atomic number = 20) to form a divalent halide.

    January 10, 2023

    General Science Questions and Answers PDF

    October 20, 2022

    When Conc. H2SO4 was added to an unknown salt in a test tube, and a brown gas (A) was evolved. This gas intensified when copper turnings were added to the test tube. On cooling gas (A) changed into a colorless gas (B). Identify the gases ‘A’ and ‘B’. Write the equations for the reactions involved.

    October 19, 2022

    Carbon and Its Compounds

    By Dr. Vikas JasrotiaJanuary 23, 2023

    CARBON AND ITS COMPOUNDS Carbon plays a very important role for all living beings. The…

    Class 10

    An element X (atomic number = 17) reacts with an element Y (atomic number = 20) to form a divalent halide.

    By Dr. Vikas JasrotiaJanuary 10, 2023

    Que. An element X (atomic number = 17) reacts with an element Y (atomic number…

    General Knowledge

    General Science Questions and Answers PDF

    By Dr. Vikas JasrotiaOctober 20, 2022

    General Science Questions and Answers PDF General Science Questions and Answers PDF Que 1. Which…

    Advertisement
    Advertisement
    Facebook Twitter Instagram Pinterest YouTube
    • Disclaimer
    • Contact Us
    • Privacy Policy 
    • Terms and Conditions
    © 2023 All Rights Reserved ScienceMotive.

    Type above and press Enter to search. Press Esc to cancel.