All 9 numericals of 9th Class Chemistry Chapter 2, Atomic Structure, solved step by step: Given Data, To Find, Formula, Calculation and Result, the way you write them in the exam. Punjab Board new syllabus.
Each numerical in the order you write it in the exam: Given Data, To Find, Formula, Calculation, Result.
Calculate the number of neutrons, protons and electrons in barium, ¹³⁷₅₆Ba.
56 protons, 56 electrons, 81 neutrons
Calculate the number of neutrons, protons and electrons in ¹⁹⁵₇₈Pt, ⁵⁵₂₅Mn and ¹²⁷₅₃I.
Pt 78 p, 78 e, 117 n; Mn 25 p, 25 e, 30 n; I 53 p, 53 e, 74 n
How many neutrons are present in ²¹⁰₈₃Bi?
127 neutrons
Krypton has five isotopes: ⁸⁰Kr 2.0 %, ⁸²Kr 12.0 %, ⁸³Kr 12.0 %, ⁸⁴Kr 57.0 % and ⁸⁵Kr 17.0 %. Calculate its relative atomic mass.
RAM of krypton ≈ 83.7
Note: The book's working prints "85 × 57.0" for the last term; it must be 17.0 (from the table) to give 83.7.
Calculate the relative mass of the light isotope of chlorine when the relative atomic mass of chlorine is 35.45, the abundance of Cl-37 is 24.23 % and that of the light isotope is 75.77 %.
Mass of the light isotope ≈ 34.95 (chlorine-35)
Calculate the relative atomic mass of lead (Pb). The isotopic abundances of ²⁰⁴Pb, ²⁰⁶Pb, ²⁰⁷Pb and ²⁰⁸Pb are 2.0, 24.0, 22.0 and 52.0 % respectively.
RAM of lead ≈ 207.2
Find the relative atomic mass of mercury: ¹⁹⁶Hg 0.0146 %, ¹⁹⁸Hg 10.02 %, ¹⁹⁹Hg 16.34 %, ²⁰⁰Hg 23.13 %, ²⁰¹Hg 13.22 %, ²⁰²Hg 29.80 %, ²⁰⁴Hg 6.85 %.
RAM of mercury ≈ 200.6
Note: The book's abundances total 99.37 %, so dividing by 100 gives 199.4. Dividing by the real total gives 200.6, the accepted value (200.59).
Calculate the relative atomic mass of nitrogen, given the abundances of its isotopes ¹⁴N and ¹⁵N are 99.64 % and 0.35 %.
RAM of nitrogen ≈ 14.0021
Rubidium has two isotopes, ⁸⁵Rb (72.2 %) and ⁸⁷Rb. Find the percentage of ⁸⁷Rb and check the atomic mass, 85.47.
⁸⁷Rb = 27.8 %; RAM ≈ 85.6
Note: Using mass numbers gives 85.56; the exact isotopic masses (84.91 and 86.91) give the stated 85.47.
