Achieve Week 10 Question 7

[Ariella Sassover 3A]

I don't understand what makes the NH4Br an acidic salt or what makes K3PO4 a basic salt in Hw Question 7.

[Edwin Montalvo 1G]

We have to look at whether the salt is derived from weak acids or weak bases. If the salt is derived from strong acids/strong bases, then the salt will be neutral.

NH4Br is made up of NH4+ and Br-. NH4+ is derived from the weak base NH3, so it does contribute to pH (since weak acids/bases do not ionize completely) and NH4+ will react with OH- to leave free H+ ions, making the salt acidic. Br- is derived from the strong acid HBr, so it does not contribute to pH.

K3PO4 is made up of 3 K+ and PO4 3-. K+ is derived from the strong base KOH, so it does not contribute to pH. PO4 3- is derived from the weak acid HPO4 2-, so it does contribute to pH, and the PO4 3- will react with H+ to leave free OH- ions, making the salt basic. Hope this helps!

[Ariella Sassover 3A]

How do you determine which is the cation or anion in these reactions?

[N Kanuri 2E]

How do you determine which is the cation or anion in these reactions?

The cation is the species that would have a positive charge (typically metals, written first in the molecular formula) and the anion is the species that would have a negative charge (typically nonmetals, written last in the molecular formula). The cation comes from the base and the anion comes from the acid.

I hope this was helpful!

[Kaira Shibata 1E]

You have to look at the anions and cations that are in the salt. If the anion is the conjugate base of weak acid, the salt will be basic. If the cation is the conjugate acid of a weak base, then the salt will be acidic. Hope that helps!

[Isela Tamayo 3H]

you should look at the cations and the anions of it?