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#1
AP Chemistry / Re: AP chemistry unit 7 questi...
Last post by uma - April 18, 2026, 10:31:57 AMMkae the RICE table to see the final answer.
Since the question says equal numbers of moles of HCl and O2 are taken initially, we can simply assume their initial concentrations are equal.
Let the initial concentration of each reactant be 1.
R 4HCl(g) + O2�(g)⇌ 2Cl2�(g) + 2H2�O(g)
I 1 1 0 0
C -4x -x +2x +2x
E 1-4x 1-x 2x 2x
From this its clear that II and III are correct.However I can not be predicted as it depends on the value of x.
So this is not something that must always be true.
Since the question says equal numbers of moles of HCl and O2 are taken initially, we can simply assume their initial concentrations are equal.
Let the initial concentration of each reactant be 1.
R 4HCl(g) + O2�(g)⇌ 2Cl2�(g) + 2H2�O(g)
I 1 1 0 0
C -4x -x +2x +2x
E 1-4x 1-x 2x 2x
From this its clear that II and III are correct.However I can not be predicted as it depends on the value of x.
So this is not something that must always be true.
#2
AP Chemistry / Re: AP chemistry Unit 7 & 9 M...
Last post by uma - April 18, 2026, 10:08:54 AMIn this question, we are discussing ΔGand not ΔG∘because the gases are mixed under non-standard conditions. Therefore, we must compare Qp with Kp. Since Q p>K p, the reaction mixture has excess products compared with equilibrium, so the reaction shifts toward the reactants. Hence, the forward reaction is non-spontaneous at that instant, and ΔG>0.
#3
AP Chemistry / AP chemistry Unit 8 (Acids and...
Last post by uma - April 18, 2026, 09:37:56 AMHCl + NaOH → NaCl+ H2O
Step 1: Calculate mmoles of each reactant
mmol of HCl=M×mL=0.25×10.0=2.50 mmol
mmol of NaOH=M×mL=1.5×5.00=7.50 mmol
Step 2: Identify the limiting and excess reactant
Since the reaction is 1 : 1:
HCl = 2.50 mmol
NaOH = 7.50 mmol
So, HCl is the limiting reactant and NaOH is the excess reactant.
Step 3: Use an initial–final table in mmoles
HCl + NaOH → NaCl+ H2O
Initial 2.50 7.50 0 0
Final 0 5.00 2.50 2.50
After the reaction, 5.00 mmol of NaOH is left in excess.
That means the solution is basic, so calculate [OH⁻].
Step 4: Calculate the concentration of excess OH⁻
Total volume after mixing: 10.0 mL+5.00 mL=15.0 mL
[OH −]= 15.0 mL /5.00 mmol
=0.333 M
Step 5: Find pOH and pH
pOH=−log(0.333)=0.48
pH=14.00−0.48=13.52
Step 1: Calculate mmoles of each reactant
mmol of HCl=M×mL=0.25×10.0=2.50 mmol
mmol of NaOH=M×mL=1.5×5.00=7.50 mmol
Step 2: Identify the limiting and excess reactant
Since the reaction is 1 : 1:
HCl = 2.50 mmol
NaOH = 7.50 mmol
So, HCl is the limiting reactant and NaOH is the excess reactant.
Step 3: Use an initial–final table in mmoles
HCl + NaOH → NaCl+ H2O
Initial 2.50 7.50 0 0
Final 0 5.00 2.50 2.50
After the reaction, 5.00 mmol of NaOH is left in excess.
That means the solution is basic, so calculate [OH⁻].
Step 4: Calculate the concentration of excess OH⁻
Total volume after mixing: 10.0 mL+5.00 mL=15.0 mL
[OH −]= 15.0 mL /5.00 mmol
=0.333 M
Step 5: Find pOH and pH
pOH=−log(0.333)=0.48
pH=14.00−0.48=13.52
#4
AP Chemistry / Re: AP chemistry -question on ...
Last post by uma - April 17, 2026, 09:50:58 PMQuote from: Chandrasekhar on April 17, 2026, 02:34:09 PMthe question asksPerfecto!
which activation pathway shows the graph with the highest activation energy and that is endothermic
i think i got why A isn't the answer, its because that is exothermic right?
#5
AP Chemistry / AP chemistry Unit 8 (Acids and...
Last post by Chandrasekhar - April 17, 2026, 09:04:34 PMHi Mam,
I was wondering how you would approach this problem?
I was wondering how you would approach this problem?
#6
AP Chemistry / AP chemistry Unit 7 & 9 MCQ Q...
Last post by Chandrasekhar - April 17, 2026, 04:17:02 PMmam, in this question I understand that delta G is greater than zero but why is it not at standard?
#7
AP Chemistry / AP chemistry unit 7 question o...
Last post by Chandrasekhar - April 17, 2026, 03:59:51 PMmam, could you explain why the answer can't be 1, 2 and 3?
#8
AP Chemistry / Re: AP chemistry -question on ...
Last post by Chandrasekhar - April 17, 2026, 02:34:09 PMthe question asks
which activation pathway shows the graph with the highest activation energy and that is endothermic
i think i got why A isn't the answer, its because that is exothermic right?
which activation pathway shows the graph with the highest activation energy and that is endothermic
i think i got why A isn't the answer, its because that is exothermic right?
#9
AP Chemistry / Re: AP chemistry -Question on ...
Last post by uma - April 16, 2026, 10:54:21 PM∆Grxn 0 = ∑[∆Gf(S) 0 + ∆Gf(O2) 0 ] - 2∆GSO3 0 = [2*0 +0] –[2*-370.4]
Now ΔGf0of any element in its stable form is zero.
For S and O2 it is zero and plug in the value of SO3 to get the answer.
Now ΔGf0of any element in its stable form is zero.
For S and O2 it is zero and plug in the value of SO3 to get the answer.
#10
AP Chemistry / Re: AP chemistry -question on ...
Last post by uma - April 16, 2026, 10:40:40 PMIt is from reactant to the top of the hill.Can you post the complete question?
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