1)copper has two naturally occurring isotopes copper 63 has an atomic mass of 62. 9 296 u and an abundance of 69. 1 5% what is the atomic mass of the second isotopic if the average atomic weight of copper is 63?

Q. An element has the following natural abundances and isotopic masses: 90.92% abundance with

19.99 amu

, 0.26% abundance with

20.99 amu

and 8.82% abundance with

21.99 amu

. Calculate the average atomic mass of this element.

Q. There are two isotopes of an element with atomic mass

z

. Heavier one has atomic mass

z + 2

and lighter one has

z - 1

, then an abundance of lighter one is:

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An element (X) has two naturally occurring isotopes 90X has an abundance of 75% and 94X has an abundance of 25%. What is the average atomic mass of element X?

The correct option is B 91 amu The average atomic mass=[ atomic mass of 90X×abundance of 90X]+[ atomic mass of 94X×abundance of 94X]abundance of 90X+abundance of 94X=[90 ×75 ]+[ 94×25 ]75 + 25= 91 amu

An element ( $X$ ) has two naturally occurring isotopes $^{90} X$ has an abundance of $75$ % and $^{94} X$ has an abundance of $25$ %. What is the average atomic mass of element $X$ ?

The correct option is B $91 a m u$
The average atomic mass
$= \frac{[{atomic mass of}^{90} X \times {abundance of}^{90} X] + [{atomic mass of}^{94} X \times {abundance of}^{94} X]}{{abundance of}^{90} X + {abundance of}^{94} X} = \frac{[90 \times 75] + [94 \times 25]}{75 + 25} = 91 amu$