Gen. Chem ?

[denttiger]

1.) Which reaction will not proceed?
A. Li + CuCl2 -->
B. Zn + NaNO3 -->
C. CaCO3 + HCl -->
D. K + H20 -->
E. H + OH -->

Can someone explain to me why the answer is "B" please?

2.) Which salt is the most soluble in water?

Answer they give is CaSO4... I thought at SO42- were soluble except Ca, Ba, Sr, and Pb... or do I have this backwards?

Thanks!

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[thefifthbeatle]

1.) Which reaction will not proceed?
A. Li + CuCl2 -->
B. Zn + NaNO3 -->
C. CaCO3 + HCl -->
D. K + H20 -->
E. H + OH -->

Can someone explain to me why the answer is "B" please?

Thanks!

OK...First off, we know that D and E work...Potassium is highly explosive in water, and H and OH form water.

This leaves us with A B and C...C is a Acid/Base rxn, obviously works.

B does not proceed because transition metals cannot replace group IA IIA metals. Group IA and IIA will replace transition metals like in A...There might be some exceptions, I forget, though...but generally, Group IA IIA can't be replaced by transition metals.

 

[denttiger]

Ahh.. that rule rings a bell. Thanks a TON! I never saw that in kaplan.. maybe i skimmed over it.

 

[PD3]

B does not proceed because transition metals cannot replace group IA IIA metals. Group IA and IIA will replace transition metals like in A...There might be some exceptions, I forget, though...but generally, Group IA IIA can't be replaced by transition metals.

But Cu is a transition metal. Why can it replace Li?

 

[dev9036]

But Cu is a transition metal. Why can it replace Li?

Why dont you look at electropotentials for each oxidation reaction thre. if you study that you will conclude that Li will be oxidized in first reaction and that's what the reaction says. but for be they say oxidation of Zn it oxi. potential is +o.76 while Na 's oxidation potn. is +2.71..... so in that reaction Na should be oxidized not Zn....

 

[dev9036]

2.) Which salt is the most soluble in water?

Answer they give is CaSO4... I thought at SO42- were soluble except Ca, Ba, Sr, and Pb... or do I have this backwards?

Thanks!

The trend for the solubility for IIA element keeps changing.. here you have a real big anion So(4)~2- So the solubilty increases with smaller Positive ions... so Ca is Soluble but not, Ba and Sr....

If you have OH~(-1) ion than ur trend was rite that solubility increases with the increasing positive ion's radius. BeCOZ OH-1 Ion is very smaller than So42-

 

[dtran1208]

1.) Which reaction will not proceed?
A. Li + CuCl2 -->
B. Zn + NaNO3 -->
C. CaCO3 + HCl -->
D. K + H20 -->
E. H + OH -->

Can someone explain to me why the answer is "B" please?

the easiest, most correct way to think about this question is by knowing the activity series for displacement reactions. the answer is B because Zn is lower on the activity series than Na, and so is unable to displace it.

if we look at the other answers, and their sequence on the activity series, we could also determine why they all occur. in A, Li is the highest on the activity series, so it can displace most other elements in a displacement reaction. in answer C, Ca is one of the elements that is able to displace hydrogen from a non-oxidizing acid (in this case, HCl), so this rxn happens. in the case of answer D, K is one of only 5 elements able to displace H from water; so this reaction also occurs. hope this helps

 

[doc toothache]

1.) Which reaction will not proceed?
A. Li + CuCl2 -->
B. Zn + NaNO3 -->
C. CaCO3 + HCl -->
D. K + H20 -->
E. H + OH -->
Can someone explain to me why the answer is "B" please?

2.) Which salt is the most soluble in water?
Answer they give is CaSO4... I thought at SO42- were soluble except Ca, Ba, Sr, and Pb... or do I have this backwards?
Thanks!

The first question has been addressed previously. Check out the activity series.

http://forums.studentdoctor.net/showpost.php?p=5013740&postcount=6

http://antoine.frostburg.edu/chem/senese/101/redox/faq/activity-series.shtml

The most "soluble" is CaSO4 with limited solubility (s.p.=6.1 x 10 e-5)

 

[denttiger]

wow! a big thanks to all of you!!!