Question

Magnesium has three naturally occurring isotopes(Mg-24, Mg-25, and Mg-26). The atomic mass and natural abundance of Mg-24 are 23.9850amu and 79 %, respectively. The atomic mass and natural abundance of Mg-25 are 24.9858amu and 10 %, respectively.Find the natural abundance of Mg-26.Express your answer using two significant figures.Find the atomic mass of Mg-26.Express your answer using two significant figures.

Answer 1

Answer:

The answer to your question is below

Explanation:

Data

               Atomic mass               Abundance

Mg -24 =    23.9850                         79%

Mg -25 =    24.9858                         10%  

Mg - 26=          ?                                  ?

Process

1.- Find the abundance of Mg-26

The sum of the abundance of the three isotopes equals 100%

         

 Abundance Mg-24 + Abundance-Mg-25 + Abundance-26 = 100

            79 + 10 + Abundance-26 = 100

            Abundance Mg-26 = 100 -89

           Abundance Mg-26 = 11%

2.- Find the atomic mass of Mg-26, the average atomic mass is 24.31 amu

Average atomic mass = (abundance)(atomic mass- 24) + (abundance)

                                         (atomic mass-25) + (abundance)(atomic mass-26)

    24.31 = (0.79)(23.9850)+ (0.10)(24.9858) + (Atomic mass-26)(0.11)

    24.31 = 18.94815 + 2.4986 + 0.11(atomic mass-26)

    24.31 = 21.4342 + 0.11(atomic mass- 26)

    0.11(atomic mass-26) = 24.31 - 21.4342

    0.11(atomic mass-26) = 2.8758

    Atomic mass-26 = 2.8758/0.11

    Atomic mass-26 = 26.1436 amu

Answer 2

Answer:

The atomic mass of Mg-26 is 25.9843 amu and has a natural abundance of 11%

Explanation:

Step 1: Data given

Isotopes of Magnesium:

⇒ Mg - 24 = 23.9850 amu ⇒ 79 %

⇒ Mg - 25 = 24.9858 amu ⇒ 10%

⇒ Mg - 26 = ? amu ⇒ 11 %

atomic mass of magnesium = 24.305 amu

0.79 * 23.9850 + 0.10 * 24.9858 + 0.11 * x = 24.305

18.94815 + 2.49858 +0.11x =24.305

0.11x = 2.85827

x = 25.9843 amu

The atomic mass of Mg-26 is 25.9843 amu and has a natural abundance of 11%