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Suppose that A and B form the compounds B₂A₃ and B₂A₃.If 0.05 mole of B₂A₃ weighs 9gm and 0.1 mole of B₂A weighs 10gm , the atomic weight of A and B respectively are

(a) 70 and 25
(b) 50 and 20
(c) 40 and 30
(d) 30 and 40

User Charkan
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1 Answer

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Final answer:

The atomic weights of elements A and B are determined by using the given mass of compounds and the number of moles provided. By setting up and solving a system of linear equations using the molar masses of B₂A₃ and B₂A, we find that the atomic weight of A is 30 amu and of B is 40 amu.

Step-by-step explanation:

Finding the Atomic Weights of Elements A and B

To calculate the atomic weights of elements A and B from the given compounds B₂A₃ and B₂A, we apply concepts like the Law of Definite Proportions and the Law of Conservation of Mass. The molar mass of a compound is numerically equivalent to its formula weight in amu, an example being the reference isotope 12C, which has both a molar mass and atomic mass of 12 g/mol or 12 amu respectively.

Given that 0.05 moles of B₂A₃ weigh 9 grams, we can divide the total mass by the number of moles to find the molar mass (MM) of B₂A₃: (9 g / 0.05 mol) = 180 g/mol. For the compound B₂A, since 0.1 mole weighs 10 grams, its MM is (10 g / 0.1 mol) = 100 g/mol.

Using these molar masses, we can set up the following equations to solve for the atomic weights of A and B:

  1. 2(B) + 3(A) = 180
  2. 2(B) + 1(A) = 100


By solving this system of linear equations, we find that the atomic weight of A is 30 amu and the atomic weight of B is 40 amu respectively.

User Ian P
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