# chemistry

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The element rhenium (Re) has two naturally occurring isotopes, 185Re and 187Re, with an average atomic mass of 186.207 amu. Rhenium is 62.60% 187Re, and the atomic mass of 187Re is 186.956 amu. Calculate the mass of 185Re.

am i supposed to multiply the atomic masses and the percents or something?
im lost..

• chemistry -

yes. Both multiply AND something.
0.6626*X + 0.3740(186.956) = 186.207
Make sure I have these paired right.
X stands for amu Re185. Solve for X.

• chemistry -

Multiply decimal percent of amu 185 and decimal percent of amu 187, add them together and you should get 186.207.

• chemistry -

shouldnt it be .626(186.956)+.374*X=186.207

• chemistry -

yes, I don't know why I typed in 6626. It should be 0.626 and 0.374. Neither do I know why I reversed the order when I typed it in BUT I'm glad I put in the post to check my pairings. According to my notes, I have
0.374(X) + 0.626(186.956) = 186.207 which I think agrees with what you have.
My eyesight is not that great as you can tell.

• chemistry -

x=186.207-(0.626)(186.956)/0.374=184.953

• chemistry -

where is the 0.3740 coming from

• chemistry -

The 0.374 comes from taking 100 percent and subtracting the 62.60% from it which gives you 37.4 percent, divide by 100 to get 0.374, now multiply by x and solve as listed above.

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