Problems like these are somewhat tricky. Yes, the mass of the Br-79 isotope is 78.9183. Bromine has only two naturally occurring isotopes Br-79 and Br-81. Br-81 is 49.31% abundant. Knowing this we can determine Br-79's percent abundance. We determine Br-79's percentage abundance by taking 100.00% and subtracting 49.31%. We can do this safely because all % are out of 100 and we know that there are only two Bromine isotopes. When the math problem has been worked out, we conclude that Br-79 is 50.69% abundant. 100.00% - 49.31% = 50.69% If we start to do weighted averages (the way these problems are solved), we end up with this: Isotope - Weight amu - Percentage Abundance Br-79 - X amu - 50.69% Br-81 - 80.9163 amu - 49.31% Amu means Atomic Mass Unit. We need to solve for x Now, when we begin our weighted average problems we must convert our percentages to decimal form. To do this we divide each percent by 100. (Simply move the decimal place two points to the left.) 50.69/100 = .0569 and 49.31/100 = .4931 With this information, we can set up an equation. Letting X = the Amu weight of Br-79. Also, recall that our average atomic mass for Br = 79.904 (from periodic table). This equation looks like this, (Mass in Amu of Br-81) * (percentage abundance in decimal of Br-81) + (X mass in amu of Br-79) * (percentage abundance in decimal of Br-79) = 79.904. Or simply (80.9163)(.4931) + (X)(.5069) = 79.904. To solve this we need to get x by itself. Step 1 Multiply 80.9163 by .4931 Our equation now looks like: (39.89982753) + (X)(.5069) = 79.904 Step 2 Subtract 39.89982753 from each side. Remember what we do to one side must be done to the other. 39.89982753 + (X)(.5069) = 79.904 -39.89982753 - 39.89982753 Now our equation is: (X)(.5069) = 40.00417247 Step 3 Divide each side by .5069 to get x by itself. The equation then looks like this (X)(.5069) = 40.00417247 (.5069) = (.5069) Then X = 78.91925916 Depending on the calculator used, and where a person rounds the answers may vary slightly. This problem if it came from where I think it came needs to be rounded to 4 sig figs. If done properly when rounded the answer is 78.91 amu.
To find the mass of Br-79, you subtract the difference in mass between Br-81 and Br-79 from the mass of Br-81.
Mass of Br-81 = 80.9163 amu Mass of Br-79 = Mass of Br-81 - (Mass of Br-81 - Mass of Br-79) = 80.9163 - (80.9163 - 78.9183) = 78.9183 amu
I don’t know
Find out the density and apply it (you cannot know otherwise)
you can find it by mercury in thermometer and spread it on the Jewel
Weigh it in water and out of water. Hmm, ok, you have to know its volume.
i know that its 3 but i only can find 2 of them !
o my goodness does anyone know where i can find this answer? o my goodness does anyone know where i can find this answer? o my goodness does anyone know where i can find this answer? o my goodness does anyone know where i can find this answer? o my goodness does anyone know where i can find this answer? o my goodness does anyone know where i can find this answer?
i don't know but when you find out let me know i don't know but when you find out let me know
you can find the distance when you know your speed and the time you traveled
i dont relly know but i would like to find out i dont relly know but i would like to find out i dont relly know but i would like to find out
be friends with him and get to know him that's how your gonna find out who he is
I have aspire one but i don't know where i find the reference no?
i dont know go find it for me! i dont know go find it for me!
You Know Where to Find Me - 2010 was released on: USA: April 2010
type in some of the lyrics that you do know and you will find something
I dont Know sorry im trying to find it too. if i find them ill let u know
Be honest and say that you do not know the answer, but will find it out and get back to you asap. i find this works well in a classroom when a child asks a question that i do not know the answer to. make sure you do find out the correct answer.
When you find out - let me know