2ne1

7+ Year Member
Oct 27, 2009
106
0
141
Status
Pre-Dental
A solution of Na2CO3 is basic. Which of the following rxns makes the solution basic?

a) Na+ (aq) + H2O -> NaOH(aq) + H+ (aq)

b) CO3^-2 (aq) + H2O -> HCO3^- + OH- (aq)

c) Na+ (aq) + H2O -> NaH(aq) + OH-

d) H2O -> H+(aq) + OH-(aq)

e) HCO3^- -> CO3^-2 + H+

Another Q

A solution of potassium acetate (KC2H3O2) in water is

a) basic because acetic acid molecules are formed
b) basic because KOH molecules are formed
c) acidic because acetic acid molecules are formed
d) acidic because KOH molecules are formed
e) neutral because potassium acetate is a salt


Thanks!
 
Last edited:

loveoforganic

-Account Deactivated-
10+ Year Member
Jan 30, 2009
4,222
12
0
Status
1) B. Not sure I have a great explanation... Just a simple acid base reaction. Where's your problem lie?

2) B is the best answer, but A is valid too.
 

2ne1

7+ Year Member
Oct 27, 2009
106
0
141
Status
Pre-Dental
the answer to the second q is A. I thought it was B...

I have another similar Q.

Which gives the most basic solution when dissolved in water?

a) H3PO4
b) NaH2PO4
c) P2O5 ??( cant really read the subscript..)
d) NaNO3
e) P2O5Na3PO4

I am just lost how to deal with these questions. Anyone willing to explain how to do these probs? Thank yoU!
 
Dec 14, 2009
423
1
0
Status
Pre-Dental
hmm interesting questions. Need Someone to explain those all 3 questions above posted !
 

K Niner

7+ Year Member
Jul 11, 2009
174
4
141
Status
Dentist
A solution of Na2CO3 is basic. Which of the following rxns makes the solution basic?

a) Na+ (aq) + H2O -> NaOH(aq) + H+ (aq)

b) CO3^-2 (aq) + H2O -> HCO3^- + OH- (aq)

c) Na+ (aq) + H2O -> NaH(aq) + OH-

d) H2O -> H+(aq) + OH-(aq)

e) HCO3^- -> CO3^-2 + H+

Another Q

A solution of potassium acetate (KC2H3O2) in water is

a) basic because acetic acid molecules are formed
b) basic because KOH molecules are formed
c) acidic because acetic acid molecules are formed
d) acidic because KOH molecules are formed
e) neutral because potassium acetate is a salt


Thanks!
1 B
2 A (acetic acid forms by grabbing a proton from solution which causes more OH to form. KOH does not form b/c both are dissolved molecules in solution. Aka K+ and OH- (aqueous)
 

UndergradGuy7

10+ Year Member
Jun 23, 2007
897
2
241
Status
Pre-Dental
#1. A solution of Na2CO3 is basic. Which of the following rxns makes the solution basic?

Na2CO3 dissociates in water to make 2 Na+ and CO3^2-. You might be tempted to think Na+ reacts with OH- from water to make NaOH, but remember NaOH is a strong base. If NaOH is a strong base the forward reaction is very favored. NaOH + H2O -> H3O+ + Na+ and OH-
The reverse reaction is not favored at all. Na+ does not react with OH- again to make NaOH.

So this leaves CO3^(2-) and you write the typical acid base reaction.
A- + H2O -> AH + OH- or CO3^2- + H2O -> HCO3^- + OH-

For 2.. A
KC2H3O2 + H2O -> HC2H3O2 (a carboxylic acid) + OH- + K+
Same reason as above. K does not recombine with OH-, but we form a weak carboxylic acid. It is a weak acid and we also form OH- so the OH- is more basic and beats the carboxylic acid.


Someone correct me if I am wrong.
 
Last edited:

loveoforganic

-Account Deactivated-
10+ Year Member
Jan 30, 2009
4,222
12
0
Status
P2O5 reacts with water to form phosphoric acid.