Anewly discovered element, y, has two naturally occurring isotopes. 87.8 percent of the sample is an isotope with a mass of 267.8 u, and 12.2 percent of the sample is an isotope with a mass of 269.9 u. what is the weighted average atomic mass for this element? 267.9 u 268.1 u 268.9 u 269.1 u

Answer :  The average atomic mass of this element is, 268.1 u

Explanation :

Average atomic mass of an element is defined as the sum of masses of each isotope each multiplied by their natural fractional abundance.

Formula used to calculate average atomic mass follows:

For isotope-1 :

Mass of isotope-1 = 267.8 amu

Fractional abundance of isotope-1 = 87.8 % = 0.878

For isotope-2 :

Mass of isotope-2 = 269.9 amu

Fractional abundance of isotope-2 = 12.2 % = 0.122

Putting values in equation 1, we get:

Thus, the average atomic mass of this element is, 268.1 u

so here we go

atomic mass

239 + 1 = y + 134 + 3 combine like terms

240 = y + 137             subtract 137 from both terms

240 - 137 = y

103 = y

atomic number

94 = z +54 + 0

94 = z + 54               subtract 54 from both sides.

40 = z

answer

a. energy is absorbed in the reaction.

if in a given reaction the energy of products is greater than the energy of reactants it means that reaction is endothermic and during the reaction, the energy is absorbed by reactants. in an endothermic reaction, the products have more stored chemical energy than the reactants. and in this reaction the reactants are more stable than products before the compounds with less energy are always more stable.