Will \(0.10 M\) solutions of the following salts be acidic, basic, or neutral? See Appendix 5 for \(K_{\mathrm{a}}\) values. a. ammonium bicarbonate b. sodium dihydrogen phosphate c. sodium hydrogen phosphate d. ammonium dihydrogen phosphate e. ammonium formate

In this step, we will identify the anions and cations for each salt and look up the \(K_{\mathrm{a}}\) values in Appendix 5. a. ammonium bicarbonate: NH4+ (cation) and HCO3- (anion) b. sodium dihydrogen phosphate: Na+ (cation) and H2PO4- (anion) c. sodium hydrogen phosphate: Na+ (cation) and HPO4^2- (anion) d. ammonium dihydrogen phosphate: NH4+ (cation) and H2PO4- (anion) e. ammonium formate: NH4+ (cation) and HCOO- (anion)

In this step, we will decide the acid/base character of each ion, using their \(K_{\mathrm{a}}\) or \(K_{\mathrm{b}}\) values as appropriate. Recall that \(K_{\mathrm{a}}\) and \(K_{\mathrm{b}}\) are related by \(K_{\mathrm{a}}\times K_{\mathrm{b}}=K_{\mathrm{w}}=10^{-14}\). (a) NH4+ is a weak acid with \(K_{\mathrm{a}}\approx5.6\times10^{-10}\). HCO3- is an amphoteric ion (it can act as an acid or a base); it has the acidic dissociation constant \(K_{\mathrm{a1}}\approx4.8\times10^{-11}\) and its conjugate base, CO3^2-, has \(K_{\mathrm{b}}\approx 2.1\times10^{-4}\). (b) Na+ is a neutral ion and does not affect acidity and basicity directly. H2PO4- is a weak acid with \(K_{\mathrm{a}}\approx6.2\times10^{-8}\). (c) Na+ is a neutral ion. HPO4^2- is the conjugate base of a weak acid (H2PO4-) with \(K_{\mathrm{b}}\approx 2.4\times10^{-13}\). (d) NH4+ is a weak acid with \(K_{\mathrm{a}}\approx5.6\times10^{-10}\). H2PO4- is a weak acid with \(K_{\mathrm{a}}\approx6.2\times10^{-8}\). (e) NH4+ is a weak acid with \(K_{\mathrm{a}}\approx5.6\times10^{-10}\). HCOO- is the conjugate base of a weak acid, formic acid, and has \(K_{\mathrm{a}}\approx1.77\times10^{-4}\).

In this step, we will compare the acidity and basicity of the anions and cations, and classify the resulting salt solutions as acidic, basic, or neutral. a. NH4+ and HCO3- both can act as weak acids, but HCO3- can also act as a weak base. Given that the \(K_{\mathrm{a}}\) value of NH4+ is larger than the \(K_{\mathrm{a1}}\) value of HCO3- and the \(K_{\mathrm{b}}\) value of HCO3- is much larger than the \(K_{\mathrm{a}}\) value of NH4+, the overall solution may be slightly basic. b. Na+ does not affect acidity/basicity. H2PO4- is a weak acid and will contribute protons to the solution, making it acidic. c. Na+ does not affect acidity/basicity. HPO4^2- is the conjugate base of a weak acid and will create an equilibrium for accepting protons, making the overall solution slightly basic. d. Both NH4+ and H2PO4- are weak acids with \(K_{\mathrm{a}}\) values close to each other, so their acidic characters will add up, making the overall solution acidic. e. NH4+ is a weak acid and HCOO- is the conjugate base of a weak acid, having a \(K_{\mathrm{a}}\) much larger than that of NH4+. Therefore, the basic character of HCOO- will dominate, and the overall solution will be basic. So, the final answer is: a. basic b. acidic c. basic d. acidic e. basic