Thursday

August 27, 2015
Posted by **Chris** on Thursday, February 8, 2007 at 12:48pm.

how do I answer this?

You know the mass of an electron. Calculate how many are in 1 gram. You will need the same number of protons. Knowing the mass of a proton calculate the number required. Post your work if you get stuck and explain what you don't understand.

- Chemisry -
**stephanie**, Saturday, January 30, 2010 at 10:22pmI don't understand what you do after you find out how many electrons are in 1 gram?

- Chemisry -
**James**, Thursday, January 8, 2015 at 4:04pm1.67262 * 10^-27 Kg is the mass of a proton. Converting that to grams, I multiply by 1000 to get 1.67262 *10^-24 grams. Since it takes 1 electron to balance 1 proton, I get the mass of 1 electron which is 0.00091 * 10^-27 Kg. Because I converted the proton's mass to grams, I have to convert the electron's mass to grams. Multiplying the mass of the electron times 1000 I get 0.00091 * 10^-24 grams. Finally, since we only want to know how much mass of an electron it takes to balance only 1 gram of a proton (not 1.67262 * 10^-24 grams), I divide the electron mass in grams by the grams of the proton to bring it to the 1 gram of proton. So 0.00091 * 10^-24/(1.67262 * 10^-24). This gives me the correct answer (confirmed by book) of 0.000544057 which when moving the decimal to the right makes it 5.44057 * 10^-4 grams or approximately 5.4 * 10^-4 grams. PLEASE NOTE: It is necessary to place the parentheses around the mass of the proton in grams you're dividing since it's in scientific notation (otherwise convert it to decimal notation first). The reason for this is that the calculator is going to attempt to divide 0.00091 * 10^-24 by 1.67262 and THEN multiply that by 10^-24. This will produce an incorrect result. The multiplication of 1.67262 * 10^-24 must be done before the division, which the calculator will do if the parentheses are places around it as shown (remember the PEMDAS and left to right rule for solving mathematical equations: Parentheses then Exponents then Multiplication OR division (whichever is first from working left to right) then Addition OR subtraction (whichever is first working from left to right)

- Chemisry -
**James**, Thursday, January 8, 2015 at 9:29pmI answered the wrong question. The answer I gave was to the question "What mass of electrons would be required to just neutralize the charge of 1.0 g of protons. We can use the same formula, however, as I stated with the difference that we divide the mass of protons by the mass of the neutrons instead of vise versa. If this were written as an algebraic equation, we'd write the two masses equal to one another (since they do have the same electrical charge) as follows:

(1.67262 * 10^-24)P = (0.00091 * 10^-24)E

Now, we'd convert the electron's mass to 1 gram by dividing the mass number by itself.

(0.00091 * 10^-24)/(0.00091 * 10^-24) and this will give us 1/1 gram of electrons

And what we do to one side of the equation we must do to the other to keep it equal. So:

(1.67262 * 10^-24)/(0.00091 * 10^-24) and this will give us 1838.043956/1 grams or just 1838.043956 grams of protons

As stated before, be sure to put the parentheses around the divisor when using the calculator so that it will be sure to calculate the multiplication first before dividing.

- Chemisry -
**James**, Thursday, January 8, 2015 at 9:35pmtest