Please help explain pH related problems in chemistry to me! Having a hard time with equivalence points and pKa values!?

Posted on 2016-04-21 18:09:00 in Chemistry by VANIS

Any explanations I would be HUGELY GRATEFUL FOR, as I have been struggling with these for a while! 
Here are some questions, that I have a hard time solving 

- If 25.00 mL of a 0.200 mol L-1 solution of the weak acid HOCl (hypochlorous acid) was titrated with 0.200 mol L-1 NaOH, what would be the pH at the equivalence point? (pKa (HOCl) = 7.52, pKw = 14) 

- 2.00 mol of Fe3O4(s) and 3.00 mol of CO(g) are placed in an evacuated container and the 
system was allowed to come to equilibrium at 575 K. The following reaction takes 
place. 
Fe3O4(s) + 4CO(g) ⇌ 3Fe(s) + 4CO2(g) 
At equilibrium it was found that 1.00 mol of CO(g) remained. Calculate the amount of Fe(s) 
present in the container at equilibrium. 

- What is the final pH of a solution formed by mixing 20.0 mL of 0.10 mol L-1 HCl with 
30.0 mL of 0.10 mol L-1 NaOH at 298 K? pKw (298 K) = 14.0 

- What is the pH of 1.0 L of a solution containing a mixture of 0.10 mol HCl and 0.10 mol 
CH3COOH (pKa = 4.74)? 

- The pH of a buffer solution prepared by mixing 12 mL of a 0.10 mol L-1 solution of HCOOH 
(pKa = 3.74) with 8 mL of a 0.10 mol L-1 solution of NaOH is: 

- For the equilibrium reaction 
Br2(g) + Cl2(g) ⇌ 2BrCl(g) Kc = 7.2 
In one reaction, the equilibrium concentrations of Br2(g) was found to be 0.065 mol L-1 and that of Cl2(g) was found to be 0.035 mol L-1. What was the equilibrium concentration of BrCl? 

Thank you very much for any help that you have provided!

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