chemistry - how to calculate average atomic mass?
955650
Do you have the percentage abundances of the isotopes?\nE.g. for chlorine, it exists as 2 isotopes, namely Cl-37 and Cl-35.\nCl-37 (with 17 protons and 20 neutrons) has an abundance of 25% with Cl-35 (with 17 protons and 18 neutrons) has an abundance of 75%.\nThus average relative atomic mass of chlorine\n= [(25/100) x 37] + [(75/100) x 35]\n= 35.5\n\nHope this helps :)
908504
Take 100 g of natural Cu, then if x is the mass of the isotope with atomic mass 62.930, the mass of the isotope with atomic mass 64.928 must be (100 - x) g. So we have the equation:\n\n62.930*x/100 + 64.928*(100 - x)/100 = 63.540\n\nSolving for x:\n\nx = 69.45% of the isotope with atomic mass = 62.930, and:\n\n100 - x = 100 - 69.45 = 30.55% of the isotope with atomic mass = 64.928
860672
Use Statistics\n\ntake your numbers and find the standard deviation this is your uncertainty (±.23). Average all the numbers this is your beaker mass (106.49). Beaker mass plus uncertainty is best estimate with uncertainty (106.49±0.23)
440454
the R.A.M. is the average mass of an atom of an element, taking account of its natural isotopes & their percentage abundance.\neg: the R.A.M. of CaCl2  :\n     the exam paper will give you the the R.A.M. s of Calcium-40 & Chlorine - 35.5,so the answer is,\n         = (1*40)+(2 * 35.5)\n         = 40+71\n         = 111\n     hope this helped.Cheerz!
1045065
ya , using the avogadro's number that is \n6.022 * 10 ^ 23\nits formula is \nno. of atoms if we have to find out\nthe no of atoms = given mass of the element /gram atomic mass * 6.022* 10 ^ 23
457002
That may be right, but the website just says that its 7 X 10^27-it doesnt explain how they figured it..\n\nSo lets see if we can figure how they got that number: There are 6 X 10^23 atoms per mole.  Lets say the average atom (most being hydrogen-1, followed by oxygen-16, and carbon-12) has a molar weight of 7.  So, 6 X 10^23 average atoms in the body would weigh 7 grams.  To get 70 kilograms, we have to multiply that by 10,000.  So, 2000 times 6 X 10^23 gets us about 6 X 10^27.  That's pretty close to 7 X 10^27.  I have a feeling that the real average molar weight per atom would be quite a bit smaller than 7, though.
266069
Every atom has two unique numbers: Atomic Number (Z) and mass number (A). Atomic number Z represents the number of protons in the nucleus of an atom. Mass number A represents the number of neutrons and protons in the nucleus of an atom. When atoms are expressed on a periodic table, they are written with a number on the top and a number on the bottom. Z is written on the top and A is written on the bottom. Also when elements are represented with the name and a number on the upper lefthand side corner. This number represents the electrical charge of the atom. This is the number that tells us if the atom gained or gave away electrons.\n\nTo calculate the number of protons: Simply just look at the atomic number and it is the number of protons. For example Number of protons in a sodium atom is 11.(Z=11)\n\nTo calculate the number of electrons: Subtract electrical charge of the atom from the atomic number. For example Na+1 tells us that sodium atom gave an electron away. So 11-1=10 electrons present.\n\nBut the number of electrons is equal to the number of protons when the atom is not charged.\n\nTo calculate the number of neutrons: Subtract the atomic number from the mass number. For example, to find the number of neutrons in the nucleus of a sodium atom 23-11=12 neutrons.
693553
The atomic number of an element is equal to the number of protons the element has in the nucleus of one atom.\nThe number of protons in the nucleus determine what element it is.\n\nThe atomic mass of an element is equal to the sum of number of protons and the number of neutrons in the nucleus.  The electrons around the atom are neglected since their mass is negligible, as well as the fact that atoms can form ions by gaining and/or loosing electrons even though the element is the same.
365764
Your second statement is correct, i.e proton mass+electron mass = constant mass and energy.\nok, This is with reference with another question you asked about mass defect(and chose my answer as the best, thanks). The sum of individual masses is greater than the actual mass of the atom. I am sure of this because this is what explains the stability of an atom(less energy, more stable).\nI'll give you an example which I took from my chem book\n\nMe = 0.0005486 amu(atomic mass unit)\nMp = 1.007277 amu\nMn = 1.008665 amu\nMe,Mp,Mn are masses of electron, proton and neutron respectively and 1 amu = 1.6605 x 10^-27 Kg\n\nOne He atom contains two electrons, two protons and two neutrons.\nSumming up the values of the constituents you get 4.032981amu as the expected mass of the atom.\nHowever the actual mass of the atom is 4.002603amu\nDifference = 0.030378 amu\n\nThe formula to find the binding evergy(energy required to bring the constituents together) is: mass defect x 931.48MeV\n\nHere that would be 0.030378 x 931.48 = 28.296 MeV\ni.e that is the equivalent of the mass defect in energy.\nThe '931.48' part is calculated using Einstein's formula E=mc^2.
941802
In order to do this, you need to realize what the balanced equation is really saying, and what relation that has to mass.  Your equation says that for every 4 iron atoms that react with 3 diatomic oxygen molecules, you'll produce 2 iron (III) oxide molecules.  Molecules are great and all, but that doesn't help you when you're trying to figure things out in terms of grams.  That's where Avogadro's number and the concept of the mole come into play.\n\nOn the periodic table, you'll notice that there are two numbers for each element:  the atomic number, which is the number of protons in an atom of the element; and the atomic weight (or mass), which is the total weight, in grams, of one mole (6.022 X 10^23 atoms) of that element.  (The atomic weight is also roughly equal to the total number of protons and neutrons in the most common isotope of the element.)\n\nIn order to figure out how much product you'll produce, you need to figure out how many moles of Fe you have, then work out the proportions.  Start by figuring the molar mass of each molecule in the reaction:\nFe = 55.845\nO2 = 2(15.9994) = 31.9988\nFe2O3 = 2(55.945) + 3(15.9994) = 159.8882\n\nNow figure out how many moles of Fe you have:\n4086 g/55.845 g/mol = 73.167 mol\n73.167 mol/4 mol Fe\n\nNow figure out how many moles of Fe2O3 you produce:\n(73.167/4) X 2 = 36.584 mol Fe2O3\n\nMultiply this by the molar mass of Fe2O3 to get the mass of the product:\n36.584(159.8882) = 5849.350 g Fe2O3\n\nb) Do the same thing you did in a), just substitute O2 for Fe2O3:\n(73.167/4) X 3 = 54.875 mol O2\n54.875 x 31.9988 = 1755.942 g O2
860730
Multiply moles by the molecular weight (grams per mol) to get mass (grams).
1022778
Mg2+ + 2HCl --> MgCl2 + H2 (gas)\n\nOkay, hydrogen.  As you can see in the above equation, for one atom of magnesium you'll produce two atoms of hydrogen.   \n\nLet's work out how much hydrogen you'll get in grams.\nAnd let's say that you have 1 gram of Mg.  First, what you need to do is work out how many atoms are in 1 gram of Mg.  \n\nThis is easy.  Simply:\n\n1 / atomic mass x Avagadro's constant = number of atoms.\n\nFor Mg, this equals:\n\n1 / 24.31 x 6.0221415×10^23 = 0.2477228 x 10^23 atoms.\n\nWe know that for every atom of Mg you'll produce 2 atoms of hydrogen.  So, that means you'll produce:\n\n2 x 0.2477228 x 10^23 = 0.4954456 x 10^23 atoms of hydrogen.\n\nTo work out how much 0.4954456 x 10^23 atoms of hydrogen weighs you just calculate, like this:\n\n0.4954456 / 6.0221415 x 1.008 = 0.0829 grams.\n\nAnd that's it.  1 gram of Mg will produce 0.0829 grams of hydrogen.
99720
Atomic mass is based on the average amu (atomic mass units) of C 12 therefore 35.5 amu is the average atomic weight for Cl 17
1096127
Remember few basics!!!!!\n\n1. One Mole of a substance is atomic weight, molecular weight or formula weight of a substance in grames.\n\nMolecular weight of water (H2O) is 18 so 18 gram of water is one mole\n\n2. One mole of any substance contains (Avagadros' number) 6.023 X 10^23 particles (molecules, atoms or ions)\n\n3. for converting mass into no. of particles follow the steps\n\nI. Divide the mass by molecul;ar weight . You get no. of Moles\n\nII. Multiply moles with Avagadro's No.\n\nYou get the number of particles
917127
Here's the how you do it.\n\nBalance the equation.  Element by element.\n\nThat gives you the mole ratios of  the various compounds.\n\nConvert the moles to mass using the molecular weight of each of the compounds.\n\nThat gives you the mass ratios of the various items.\n\nDivide both sides of the equation by the largest mass on the left side of the equation,    Then  you will have the mass of products per Kg of the at least one of the reactants.  Remember  you are starting with 1.0 kg of one item and 0.98 of the other.\n\nso you must check to see which reactant will limit the production.\n\nShould be a simple matter of working out the ratios.
780771
Na : atomic mass = 23\nCl : atomic mass = 35\natomic mass of compound = 58 g/mole\n350. mL = 0.35 L\n\n.376 Molar solution means 58 moles / liter\n(58 * (grams / mole)) * (.376 * (moles / liter)) * (.35 L) = 7.6328 grams
29071
Well, look in the periodic table of the elements and find the molecular weight. The molecular weight tells you how many grams are in one mole of that element. Once you know the amount of grams that correspond to 1 mole, you do the math.\nGood luck!