Question

Determination of Atomic Masses -- Historical Stanislao Cannizarro (1826-1910) applied Dalton's (1766-1844) Atomic Theory, Avogadro's (1776-1850) Hypothesis, and the experimental methods of Gay-Lussac (1778-1850), to correctly deduce relative atomic masses for various elements. For example, suppose a nameless element (X) was found to occur in three different substances (A, B and C). The relative molecular masses of A, B, and C were found to be 86.20, 136.20 and 168.50 respectively, compared to an assigned value of exactly 2.00 for H. Subsequently, these substances were subjected to elemental analysis and were found to contain 81.6%, 77.4% and 83.5% of X respectively by mass. What is the likely) relative atomic mass of X, on this scale? (Note that this is NOT the same scale as current conventional atomic mass units.) 1pts Submit Answer Tries 0/5 What would be the correct chemical symbol for X? Note that chemical symbols are case-sensitive. e.g. Helium is He not he nor HE.

Answer 1

Here is the Solution:

A nameless element (x) uas found to be occur in three df fer ent A,B,0 and their rel ative molecl qr masses are Contain 81.6% Sub st an ces A =86.20 B 136.20 77.40 C =168.5o 83.5 by mass. So, 81.6 81.6% of 86.20 is 86.20 70.3392 i DO 77.47 0f 1 36.20 77.4 x 136.20 105.4188 io0 83.5yot 168.50 8 3.5 16 8. 50= 14D.6975 100 Nouo, we have 70.3342 10C.4188, 140,6975 molecular mass A,B and respectively. where, 30. 3392 isthe smallest Mw A,A and c by Smallest molelar m9ss of Ovide 30.3392 A 1.000 0 70.3392 i05. 4188 B = 1.4987 70.3392 140.6975 = 2.0D02 70.3392 Nowo, haultiply the ratios by 2 then round to the near est fnteg er. 1.DO00 X 2 A = 2. 1.4987x 2 3 2.0002 x 2 4 Nov, dvide the fractfonal wweight attrbute to'x and take the B = C = mass. average to estimate the relatfve atomit 70.3392 35. 1696 35.1696+ 35. 1346 t35.174y 2 Average = 105.4188 35.1396 3 140.6975 3 35.16 35.1744 1 Theretore, the relative atomic mass of X X=35. 16 x .0026 2 70.36 The chemical symbol would be Ga or Cl2

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