### HW problem 12.69 (6th edition)

Posted:

**Wed Jan 23, 2019 11:23 pm**Can someone explain how to work through this problem? I understand the calculations and everything, but would I need to look up the Ka value or??

Created by Dr. Laurence Lavelle

https://lavelle.chem.ucla.edu/forum/

https://lavelle.chem.ucla.edu/forum/viewtopic.php?f=60&t=40612

Page **1** of **1**

Posted: **Wed Jan 23, 2019 11:23 pm**

Can someone explain how to work through this problem? I understand the calculations and everything, but would I need to look up the Ka value or??

Posted: **Wed Jan 23, 2019 11:29 pm**

(Sorry the tables I'm referring to are labeled this way in the 7th edition!)

Yes, for part a), you use the Kb value for NH3 in table 6C.2 to find the Ka value of its conjugate acid NH4+

(KaKb = Kw)

For part b), you can use table 6D.1 to find the Ka value of common cations in water, which includes Al3+ at 1.4 x 10^-5

Hope that helps!

Yes, for part a), you use the Kb value for NH3 in table 6C.2 to find the Ka value of its conjugate acid NH4+

(KaKb = Kw)

For part b), you can use table 6D.1 to find the Ka value of common cations in water, which includes Al3+ at 1.4 x 10^-5

Hope that helps!

Posted: **Wed Jan 23, 2019 11:32 pm**

Anusha 1C wrote:(Sorry the tables I'm referring to are labeled this way in the 7th edition!)

Yes, for part a), you use the Kb value for NH3 in table 6C.2 to find the Ka value of its conjugate acid NH4+

(KaKb = Kw)

For part b), you can use table 6D.1 to find the Ka value of common cations in water, which includes Al3+ at 1.4 x 10^-5

Hope that helps!

I guess I totally skimmed over the common cations table lol but thank you!!