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Topic: Mass percent and aqueous reactions  (Read 8149 times)

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Offline Korokian

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Mass percent and aqueous reactions
« on: October 06, 2006, 04:55:48 PM »
1) What are the mass percentages of the elemnts in KMnO4?
-I got 25%K, 35%Mn, 40%O

2) A compound has the formula XF3 and is found to contain 64.8% F by mass. What is the atomic weight of element X?
- I got 31.0 AMU

3) What volume of 0.350M HNO3 reacts completely with 42.2 mL of 0.150 M Na2CO3 in the following reactions?
- I got 18.2 mL

Can someone please tell me if those are correct?
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Offline enahs

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Re: Mass percent and aqueous reactions
« Reply #1 on: October 06, 2006, 05:24:53 PM »
1 & 2 or correct, 3 is not.
It looks like in #3 you forgot to balance the equation first, or balanced it wrong.
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Offline Korokian

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Re: Mass percent and aqueous reactions
« Reply #2 on: October 06, 2006, 06:37:26 PM »
i got 2HNO3 + Na2CO3 --> H2CO3 + 2Na(NO3)2
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Offline Borek

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Re: Mass percent and aqueous reactions
« Reply #3 on: October 06, 2006, 06:40:39 PM »
Quote from: Korokian on October 06, 2006, 06:37:26 PM
i'm lost on number 3 ... do i use Molarity x Volume= Molarity x Volume?

Almost. Remember about stoichiometric coefficient. How many moles of nitric acid reacts with 1 mole of carbonate?
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Offline Korokian

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Re: Mass percent and aqueous reactions
« Reply #4 on: October 06, 2006, 06:42:58 PM »
2 to 1? and is the answer 36.3mL??
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Offline Borek

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Re: Mass percent and aqueous reactions
« Reply #5 on: October 06, 2006, 06:50:07 PM »
Yep. Download EBAS and learn how to use it to check answers.
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Offline Korokian

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Re: Mass percent and aqueous reactions
« Reply #6 on: October 06, 2006, 06:55:18 PM »
okay , but i will avoid using it as much as possible... i don't get that software in an ap chem exam
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Offline Borek

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Re: Mass percent and aqueous reactions
« Reply #7 on: October 06, 2006, 07:00:28 PM »
Quote from: Korokian on October 06, 2006, 06:55:18 PM
okay , but i will avoid using it as much as possible... i don't get that software in an ap chem exam

Sure thing, that's just a way of checking, not solving. At least till you know what you are doing, then it is a way of saving time.
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Offline Korokian

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Re: Mass percent and aqueous reactions
« Reply #8 on: October 06, 2006, 07:02:37 PM »
Yes, thank you. One more, When .200 L of a solution of .0580M CaCl2 is treated with an excess of a solution of AgNO3, a precipitate of AgCl is formed. the mass of AgCl is..
i got 3.33g
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Offline enahs

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Re: Mass percent and aqueous reactions
« Reply #9 on: October 06, 2006, 07:12:28 PM »
Correct.
Quote from: Korokian on October 06, 2006, 07:02:37 PM
Yes, thank you. One more, When .200 L of a solution of .0580M CaCl2 is treated with an excess of a solution of AgNO3, a precipitate of AgCl is formed. the mass of AgCl is..
i got 3.33g

Yes.
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Offline Korokian

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Re: Mass percent and aqueous reactions
« Reply #10 on: October 07, 2006, 05:08:49 PM »
QUESTION, are strong the strong bases strong electrolytes?

and i don't get what this problem is asking for
Consider the following formula of species dissolved in water at room temperature.
W. NH3(aq)
X. NH4
Y. NH4Cl (aq)
Z. HCl
Which of them do not represent the major species present in the solution?

is it NH4 because it does not dissolve in water, and therefore it is at the bottom of the solution?
« Last Edit: October 07, 2006, 06:25:47 PM by Korokian »
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