posted by .

Natural rubidium has an average mass of 85.4678 amu and is composed of isotopes
85Rb (mass = 84.9117 amu) and 87Rb. The ratio of the isotopes 85Rb/87Rb in natural rubidium is 2.591. What is the mass of 87Rb?

Let x be the fraction of the Rb atoms that are Rb85. x/2.591 is the fraction that are Rb87

x + x/2.591 = 1
1.38595 x = 1
x = 0.7215 = fraction that is Rb85
1-x = 0.2784 = fraction that is Rb87
Avg mass = 85.4678 = (0.7215)(84.9117) + (0.2784)M87
Solve for M87

  • Science -

    M87 = 86.94 amu

  • Science -

    not a very good answer... I'm sure the person asking the question is looking for an answer that applies to every question, and not only to this one.

Respond to this Question

First Name
School Subject
Your Answer

Similar Questions

  1. chemistry

    This is a lengthy problem, but I really don't understand it. Any assistance given would be greatly appreciated. An analysis was done on a rock sample to determine its rubidium content. The rubidium content of a portion of rock weighing …
  2. Chemistry

    How would I solve this: The atomic mass of 6/3Li and 7/3Li are 6.0151 amu and 7.0160 amu, respectively. Calculate the natural abundances of these 2 isotopes. The average atomic mass of Li is 6.941. All I know is how to get the atomic …
  3. CHEM

    Magnesium has an average atomic mass of 24.3068 amu and has three isotopes: 24Mg(23.985045 amu), 25 Mg (24.985839 amu) and 26 Mg(25.982595 amu) The 26 Mg isotope has an abundance of 11.1%. what are the abundances of the other two isotopes. …
  4. chemistry

    Silicon has three naturally occurring isotopes: Si-28 with mass 27.9769 amu and a natural abundance of 92.21%, Si-29 with mass 28.9765 amu and a natural abundance of 4.69%, and Si-30 with mass 29.9737 amu and a natural abundance of …
  5. Chem

    Bromine has two natural occurring isotopes (Br-79 and Br-81) and has an atomic mass of 79.904 amu. The mass of Br-81 is 80.9163 amu, and its natural abundance is 49.31%. Calculate the mass and natural abundance of Br-79.
  6. physics

    The rubidium isotope 87Rb is a β emitter that has a half-life of 4.9 x 1010 y that decays into 87Sr. It is used to determine the age of rocks and fossils. Rocks containing the fossils of early animal have a ratio of 87Sr to 87Rb …
  7. Chemistry

    On another planet, the isotopes of titanium have the following natural abundances. Isotope 46Ti Abundance 70.900% Mass(amu) 45.95263 Isotope 48Ti Abundance 10.000% Mass(amu) 47.94795 Isotope 50Ti Abundance 19.100% Mass(amu) 49.94479 …
  8. Chem

    A newly discovered element, Mysternium (Atomic symbol My) has two isotopes and an average atomic mass of 296.7286 amu. One of the isotopes, My-296 has a natural abundance of 61.528% and has a mass value of 295.9064 amu. What is the …
  9. chemistry

    How much energy in MeV is released to form one atom of 87Rb from protons, electrons, and neutrons if the nucleus has a mass of 86.909187 amu?
  10. chemistry

    Magnesium has three naturally occurring isotopes: Mg-24 with mass 24.3050 amu and a natural abundance of 78.99 %, Mg-25 with mass 24.9858 amu and a natural abundance of 10.00 %, and Mg-26 with mass 25.9826 amu and a natural abundance …

More Similar Questions