# HELP! with calculating charge/mass/specific charge of an IonWatch

#1
Help me with this question please.

A 63
CU atom loses two electrons. For the ion which is formed:
29

(a) Calculate the charge in coulombs
(b) Calculate the specific charge

I know the formula for specific charge is charge OVER mass = Specific charge but i keep getting the wrong answer!

Also with this question

(a) Neglecting the mass of electrons, how many atoms of plutonium-239 atom are contained in a 1 gramme sample?

(b)How much energy in MeV and joules is released if the nucleus of plutonium-239 atom is completely converted into energy?
0
10 years ago
#2
The charge will surely just be 2 times the charge on an electron (can't remember the value off the top of my head).

For specific charge the mass will be 29 x mass of proton + 34 x mass of neutron
This what you're using?

For your second part 239 is the mass number, 239 minus atomic number of plutonium will give number of neutrons.

number of neutrons x mass of neutron + number of proton x mass of protons = mass of a single plutonium atom

Divide 1g or 0.001kg (depending on the units you're working in) by your answer above and that will give your number of atoms.

I think the second part is just E=mc^2 to get the energy released (in joules)
0
5 years ago
#3
help asap
how do you calculate the charge in coulombs and the specific charge of
48
C
20
0
5 years ago
#4
charge in coulombs is just 2 x 1.6x10^-19

specific charge is 3.2x10^-19/(63x1.67x10^-27+29x9.11x10^-31) = 3.0x10^6
0
5 years ago
#5
With specific charges of an Ion you must include the weight of the electrons, so include the weight of 27 electrons in the calculation.
0
5 years ago
#6
Help me with this question please.

A 63
CU atom loses two electrons. For the ion which is formed:
29

(a) Calculate the charge in coulombs
(b) Calculate the specific charge

I know the formula for specific charge is charge OVER mass = Specific charge but i keep getting the wrong answer!

Also with this question

(a) Neglecting the mass of electrons, how many atoms of plutonium-239 atom are contained in a 1 gramme sample?

(b)How much energy in MeV and joules is released if the nucleus of plutonium-239 atom is completely converted into energy?
Re. the first question: this question is given on page 5 of the Nelson Thornes' AQA Physics A - AS book. As per the answers given at the back it works out like this:
a) Charge of the ion formed = 2 * (+1.6 * 10^-19) = 3.2 * 10^-19 C

c) Specific Charge of the Ion = (3.2 * 10^-19) / (63 * 1.67 * 10^-27) = 3.04 * 10^6 CKg^-1
0
5 years ago
#7
(Original post by Chris654)
With specific charges of an Ion you must include the weight of the electrons, so include the weight of 27 electrons in the calculation.
At A-Level you just count the mass of an electron as 0 since it's already so low.
0
5 years ago
#8
(Original post by ImNormal)
At A-Level you just count the mass of an electron as 0 since it's already so low.
Depends which exam board. Because the mass of the electron is negligible in comparison to the mass of a proton/neutron, it wouldn't really affect the mass to charge ratio. However for AQA one mark is from the calculation, and you must include the mass of the electrons, even if you get the same answer. For example question 1)iii) on AQA June 2013 Physics 1

Have a look at what the mark scheme says.

Also just realised this post is from like 2008 haha
0
5 years ago
#9
(Original post by Chris654)
However for AQA one mark is from the calculation, and you must include the mass of the electrons, even if you get the same answer. For example question 1)iii) on AQA June 2013 Physics 1

Have a look at what the mark scheme says.

Also just realised this post is from like 2008 haha
The mark scheme actually says that you either have to include the electrons, or write that you are discounting them. I imagine a bracketed sentence to the right of your working saying (ignoring negligible mass of electrons) would suffice for the mark.
0
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