Calculate [H+] in 0.375M H2PO4 Ka=6.2x10^-8
I know I'm suppose to write the equation first, but I'm not sure if I did it right:
H2PO4 + H2O <=> 2H+ + PO4
is that right?
You need to clarify the question. Is that a salt, such as KH2PO4, that is 0.375 M or is it the ion H2PO4^-. Is the Ka listed actually k2 for H3PO4? And is this part of a larger problem? The (H^+) for a salt such as KH2PO4 is sqrt (k1*k2).
To properly calculate the [H+] concentration in a solution of 0.375 M H2PO4, we need to clarify a few points. First, it's important to understand the nature of the compound you provided. H2PO4 can exist as a salt (such as KH2PO4) or as an ion (H2PO4^-).
Assuming you are referring to the ion H2PO4^-, we can use the given Ka value of 6.2x10^-8 to determine the concentration of [H+]. However, we need additional information regarding the system and the specific form of H2PO4^-.
The equation you mentioned, H2PO4 + H2O ⇌ 2H+ + PO4, is not complete. H2PO4 behaves as both an acid and a base, which means it can donate or accept protons (H+). To fully represent the dissociation of H2PO4^- into water, the equation should be:
H2PO4^- + H2O ⇌ H3O+ + HPO4^2-
Now, if we assume that H2PO4^- is the typical monobasic acid form of dihydrogen phosphate ion, we can employ the concept of Ka to determine [H+]. However, it's worth noting that Ka value provided (6.2x10^-8) appears to be associated with the second proton dissociation constant, not the first (k2 for H3PO4).
A correct equation for the first ionization of H2PO4^- (H2PO4^- → H+ + HPO4^2-) would have a Ka value associated with k1. Double-check if you have the correct value or if there is additional information that needs to be considered for the calculation.
Assuming you have the necessary information, you could use the Ka value to calculate the concentration of [H+] in the solution. The balanced equation represents a one-to-one ratio between H2PO4^- (acid) and H+ (conjugate acid). Therefore, the initial concentration of H2PO4^- will be equal to the concentration of [H+].
If you have the correct Ka (k1) value and it is associated with H2PO4^-, you can directly substitute into the formula [H+] = sqrt(Ka * [H2PO4^-]) to calculate the concentration of [H+].
If this calculation is part of a larger problem or if there are other factors involved, please provide more context, and I will be happy to assist you further.