I have a lab report to write on an experiment titled Thermodynamics of a compoun

Question

I have a lab report to write on an experiment titled Thermodynamics of a compound. We titrated 10ml of Ca(OH)2 with 8.7 ml 0.1M HCl at room temperature. Then we heated (to boiling) a different batch and performed three titrations that took an average 0f 2.0ml HCl. We are supposed to figures out the concentrations of Ca and OH and get the ksp to use in deltaG =-RTlnKsp. We will use the room temp of 293.7K and a second time with the heated temp of 373K. Eventually we are to find entropy and gibbs free energy but I am still stuck at finding ksp. I know that the moles of hydroxide are twice the calcium .I figured the moles of HCl to be 0.0087Lx 0.1M = 0.00087 and thus equal to the moles of base at equivalence point so do I divide by 2 or multiply by 2 to get [Ca] [OH]2 to get ksp. And then I think there is another step in there. Do I use the volume of base somewhere?

Explanation / Answer

In the titration, the reaction is:

2HCl+Ca(OH)2=CaCl2+2H2O

AS Ca(OH)2 RELEASE 2 OH- IONS SO 2 MOL OF H+ ALSO REQUIRE FOR ACID BASE REACTION

The acid to base ratio is 2:1

(moles acid used) = 2 (moles base useD)

The chemical equation:

Ca(OH)2 ? Ca2+ + 2OH¯

2) The Ksp expression:

Ksp = [Ca2+] [OH¯]2

MOLES OF HCl = 0.00087

moles Ca(OH)2 titrated:

0.00086mol / 2 = 0.00043 mol

Remember, every one Ca(OH)2 titrated requires 2 H+

0.00043 mol of Ca(OH)2 in 10.0 mL means:

[Ca2+] = 0.00043 mol / 0.010 L = 0.043 M
[OH¯] = 0.00086 /0.010L =0.086 M

2) Calculate the Ksp:

Ksp = (0.043) (0.086)2

= 31.8 x 10¯5

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