The larger the Ka value, the stronger the acid. There is a simple relationship between the magnitude of \(K_a\) for an acid and \(K_b\) for its conjugate base. As such it is an important sink in the carbon cycle. $$\ce{[H3O+]} = \frac{\ce{K1[H2CO3]}}{\ce{[HCO3-]}}$$, Or in logarithimic form: Terms The concentrations used in the equation for Ka are known as the equilibrium concentrations and can be determined by using an ICE table that lists the initial concentration, the change in . HCO3 or more generally as: z = (H+) 2 + (H+) K 1 + K 1 K 2 where K 1 and K 2 are the first and second dissociation constants for the acid. The Kb value is high, which indicates that CO_3^2- is a strong base. Acids are substances that donate protons or accept electrons. TABLE OF CONJUGATE ACID-BASE PAIRS Acid Base K a (25 oC) HClO 4 ClO 4 - H 2 SO 4 HSO 4 - HCl Cl- HNO 3 NO 3 - H 3 O + H 2 O H 2 CrO 4 HCrO 4 - 1.8 x 10-1 H 2 C 2 O 4 (oxalic acid) HC 2 O 4 - 5.90 x 10-2 [H 2 SO 3] = SO 2 (aq) + H2 O HSO using the ka for hc2h3o2 and hco3 - ASE HCO3 H CO3 2 (9.20a) and 2 H c b 3 2 ' 3 2 K [HCO ] . So: {eq}K_a = \frac{[x^2]}{[0.6]}=1.3*10^-8 \rightarrow x^2 = 0.6*1.3*10^-4 \rightarrow x = \sqrt{0.6*1.3*10^-8} = 8.83*10^-5 M {/eq}, {eq}[H^+] = 8.83*10^-5 M \rightarrow pH = -log[H^+] \rightarrow pH = -log 8.83*10^-5 = 4.05 {/eq}. The plot that looks like a "XX" also allows us to see a interesting property of carbonates. In a solution of carbonic acid, we have 1) water and 2) carbonic acid in the main. Stack Exchange network consists of 181 Q&A communities including Stack Overflow, the largest, most trusted online community for developers to learn, share their knowledge, and build their careers. When HCO3 increases , pH value decreases. But it is always helpful to know how to seek its value using the Ka formula, which is: Note that the unit of Ka is mole per liter. 0.1M of solution is dissociated. Butyric acid is responsible for the foul smell of rancid butter. The conjugate base of a strong acid is a weak base and vice versa. The magnitude of the equilibrium constant for an ionization reaction can be used to determine the relative strengths of acids and bases. Examples include as buffering agent in medications, an additive in winemaking. Is this a strong or a weak acid? PDF 10 Chemistry of Carbonic Acid Equilibria in Water - Iaea 70%75% of CO2 in the body is converted into carbonic acid (H2CO3), which is the conjugate acid of HCO3 and can quickly turn into it. Its Ka value is {eq}1.3*10^-8 mol/L {/eq}. Connect and share knowledge within a single location that is structured and easy to search. A freelance tutor currently pursuing a master's of science in chemical engineering. [7], Additionally, bicarbonate plays a key role in the digestive system. The Ka equation and its relation to kPa can be used to assess the strength of acids. All chemical reactions proceed until they reach chemical equilibrium, the point at which the rates of the forward reaction and the reverse reaction are equal. Nonetheless, I believe that your ${K_a}$ for carbonic acid is wrong; that number looks suspiciously like the ${K_a}$ instead for hydrogen carbonate ion (or the bicarbonate ion). Ocean Biomes, Working Scholars Bringing Tuition-Free College to the Community. When the calcium carbonate dissolves, a equilibrium is established between its three forms, expressed by the respective equilibrium equations: First stage: The higher the Ka, the stronger the acid. Ka = (4.0 * 10^-3 M) (4.0 * 10^-3 M) / 0.90 M. This Ka value is very small, so this is a weak acid. What is the purpose of non-series Shimano components? Plug in the equilibrium values into the Ka equation. This variable communicates the same information as Ka but in a different way. Using Kolmogorov complexity to measure difficulty of problems? \[pK_a + pK_b = 14.00 \; \text{at 25C} \], Stephen Lower, Professor Emeritus (Simon Fraser U.) It is equal to the molar concentration of the ions the acid dissociates into divided by the molar concentration of the acid itself. See examples to discover how to calculate Ka and Kb of a solution. But at the same time it states that HCO3- will react as a base, because it's Kb >> Ka, True, $HCO_3^-$ will react as both an acid and a base. As we assumed all carbonate came from calcium carbonate, we can write: Bronsted-Lowry defines acids as chemical substances that have the ability to donate protons to other substances. Potassium bicarbonate is used as a fire suppression agent ("BC dry chemical") in some dry chemical fire extinguishers, as the principal component of the Purple-K dry chemical, and in some applications of condensed aerosol fire suppression. Once again, the concentration does not appear in the equilibrium constant expression.. Should it not create an alkaline solution? This is especially important for protecting tissues of the central nervous system, where pH changes too far outside of the normal range in either direction could prove disastrous (see acidosis or alkalosis). The term "bicarbonate" was coined in 1814 by the English chemist William Hyde Wollaston. Why does it seem like I am losing IP addresses after subnetting with the subnet mask of 255.255.255.192/26? [1] A fire extinguisher containing potassium bicarbonate. The bicarbonate ion (hydrogencarbonate ion) is an anion with the empirical formula HCO3 and a molecular mass of 61.01daltons; it consists of one central carbon atom surrounded by three oxygen atoms in a trigonal planar arrangement, with a hydrogen atom attached to one of the oxygens. Diprotic Acid Overview & Examples | What Is a Diprotic Acid? PDF Table of Acids with Ka and pKa Values* CLAS - UC Santa Barbara $$Cs = \ce{\frac{[HCO3-][H3O+]^2 + K1[HCO3-][H3O+] + K1K2[HCO3-]}{K1[H3O+]}}$$ $$Cs = \ce{[CaCO3]} = \ce{[H2CO3] + [HCO3-] + [CO3^2-]}$$, Where Cs here stands for the known concentration of the salt, calcium carbonate. Solved For which of the following equilibria does Kc | Chegg.com Bicarbonate also acts to regulate pH in the small intestine. The renal electrogenic Na/HCO3 cotransporter moves HCO3- out of the cell and is thought to have a Na+:HCO3- stoichiometry of 1:3. The larger the \(K_b\), the stronger the base and the higher the \(OH^\) concentration at equilibrium. We've added a "Necessary cookies only" option to the cookie consent popup. ,NH3 ,HAc ,KaKb - General Ka expressions take the form Ka = [H3O+][A-] / [HA]. and it mentions that sodium ion $ (\ce {Na+})$ does not tend to combine with the hydroxide ion $ (\ce {OH-})$ and I was wondering what prevents them from combining together to form $\ce {NaOH . Follow Up: struct sockaddr storage initialization by network format-string. Calculate \(K_a\) and \(pK_a\) of the dimethylammonium ion (\((CH_3)_2NH_2^+\)). The following questions will provide additional practice in calculating the acid (Ka) and base (Kb) dissociation constants. Bicarbonate is the dominant form of dissolved inorganic carbon in sea water,[9] and in most fresh waters. How to calculate bicarbonate and carbonate from total alkalinity \(K_a = 1.4 \times 10^{4}\) for lactic acid; \(pK_b\) = 10.14 and \(K_b = 7.2 \times 10^{11}\) for the lactate ion. Carbonic acid, $\ce{H2CO3}$, has two ionizable hydrogens, so it may assume three forms: The free acid itself, bicarbonate ion, $\ce{HCO3-}$ (first-stage ionized form) and carbonate ion $\ce{CO3^2+}$ (second-stage ionized form). Plus, get practice tests, quizzes, and personalized coaching to help you Calculate \(K_b\) and \(pK_b\) of the butyrate ion (\(CH_3CH_2CH_2CO_2^\)). Bicarbonate (HCO3) is a vital component of the pH buffering system[3] of the human body (maintaining acidbase homeostasis). Can Martian regolith be easily melted with microwaves? This is used as a leavening agent in baking. PDF Tutorial 4: Ka & Kb for Weak acids and Bases Based on the Kb value, is the anion a weak or strong base? The Ka value is very small. But at the same time it states that HCO3- will react as a base, because it's Kb >> Ka $\endgroup$ - _ The Kb value for strong bases is high and vice versa. In this case, we are given \(K_b\) for a base (dimethylamine) and asked to calculate \(K_a\) and \(pK_a\) for its conjugate acid, the dimethylammonium ion. ah2o3bhco3-ch2c03dhco3-eh2c03 It is both the conjugate base of carbonic acidH2CO3; and the conjugate acid of CO23, the carbonate ion, as shown by these equilibrium reactions: A bicarbonate salt forms when a positively charged ion attaches to the negatively charged oxygen atoms of the ion, forming an ionic compound. The acid is HF, the concentration is 0.010 M, and the Ka value for HF is 6.8 * 10^-4. We need to consider what's in a solution of carbonic acid. EDIT: I see that you have updated your numbers. NH4+ is our conjugate acid. Substituting the \(pK_a\) and solving for the \(pK_b\). Chemistry of buffers and buffers in our blood - Khan Academy The Ka expression is Ka = [H3O+][C2H3O2-] / [HC2H3O2]. But so far we have only two independent mathematical equations, for K1 and K2 (the overrall equation does't count as independent, as it's only the merging together of the other two). The acid dissociation constant value for many substances is recorded in tables. If we add Equations \(\ref{16.5.6}\) and \(\ref{16.5.7}\), we obtain the following (recall that the equilibrium constant for the sum of two reactions is the product of the equilibrium constants for the individual reactions): \[\cancel{HCN_{(aq)}} \rightleftharpoons H^+_{(aq)}+\cancel{CN^_{(aq)}} \;\;\; K_a=[H^+]\cancel{[CN^]}/\cancel{[HCN]}\], \[\cancel{CN^_{(aq)}}+H_2O_{(l)} \rightleftharpoons OH^_{(aq)}+\cancel{HCN_{(aq)}} \;\;\; K_b=[OH^]\cancel{[HCN]}/\cancel{[CN^]}\], \[H_2O_{(l)} \rightleftharpoons H^+_{(aq)}+OH^_{(aq)} \;\;\; K=K_a \times K_b=[H^+][OH^]\]. $$K1K2 = \frac{\ce{[H3O+]^2[CO3^2-]}}{\ce{[H2CO3]}}$$, Analysing our system, to give a full treatment, if we know the solution pH, we can calculate $\ce{[H3O+]}$. Because the \(pK_a\) value cited is for a temperature of 25C, we can use Equation 16.5.16: \(pK_a\) + \(pK_b\) = pKw = 14.00. All other trademarks and copyrights are the property of their respective owners. Conjugate acids (cations) of strong bases are ineffective bases. What is the pKa of a solution whose Ka is equal to {eq}2*10^-5 mol/L {/eq}? The partial dissociation of ammonia {eq}NH_3 {/eq}: {eq}NH_3(aq) + H_2O_(l) \rightleftharpoons NH^+_4(aq) + OH^-_(aq) {/eq}. Chemical substances cannot simply be organized into acid and base boxes separately, the process is much more complex than that. Sodium hydroxide is a strong base that dissociates completely in water. Ammonium bicarbonate is used in digestive biscuit manufacture. The equation then becomes Kb = (x)(x) / [NH3]. Why does Mister Mxyzptlk need to have a weakness in the comics? It only takes a minute to sign up. HCO3 and pH are inversely proportional. Nature 487:409-413, 1997). Does a summoned creature play immediately after being summoned by a ready action? The pH measures the acidity of a solution by measuring the concentration of hydronium ions. The acid and base strength affects the ability of each compound to dissociate. HCl is the parent acid, H3O+ is the conjugate acid, and Cl- is the conjugate base. I did just that, look at the results (here the spreadsheet, to whomever wants to download and play with it): We see that in lower pH the predominant form for carbonate is the free carbonic acid. It is isoelectronic with nitric acid HNO 3. 7.12: Relationship between Ka, Kb, pKa, and pKb In fact, for all acids we can use a general expression for dissociation using the generic acid HA: HA + H2O --> H3O+ + A-. We need a weak acid for a chemical reaction. In aqueous solution carbonic acid behaves as a dibasic acid.The Bjerrum plot shows typical equilibrium concentrations, in solution, in seawater, of carbon dioxide and the various species derived from it, as a function of pH. PDF CARBONATE EQUILIBRIA - UC Davis The same logic applies to bases. The most common salt of the bicarbonate ion is sodium bicarbonate, NaHCO3, which is commonly known as baking soda. Kb's negative log base ten is equal to pKb, it works the same as pKa expect that it's for bases. I feel like its a lifeline. Why does the equilibrium constant depend on the temperature but not on pressure and concentration? In a given moment I can see you in a room talking with either friend, but I will never see you three in the same room, or both friends of yours. See Answer Question: For which of the following equilibria does Kc correspond to the base-ionization constant, Kb, of HCO3? then: +2 2 3 T [ HCO ][ ]H = CZ (13) - + 3 1 T [ HCO][ ] HK = CZ (14) 2312 [] T HCOKK CZ = (15) Figure 5.1. For sake of brevity, I won't do it, but the final result will be: {eq}pK_a = - log K_a = - log (2*10^-5)=4.69 {/eq}. Again, for simplicity, \(H_3O^+\) can be written as \(H^+\) in Equation \(\ref{16.5.3}\). (Kb > 1, pKb < 1). We plug the information we do know into the Ka expression and solve for Ka. Note that a interesting pattern emerges. Your kidneys also help regulate bicarbonate. Equilibrium Constant & Reaction Quotient | Calculation & Examples. Conversely, smaller values of \(pK_b\) correspond to larger base ionization constants and hence stronger bases. The relative strengths of some common acids and their conjugate bases are shown graphically in Figure 16.5. Thus the conjugate base of a strong acid is a very weak base, and the conjugate base of a very weak acid is a strong base. [14], The word saleratus, from Latin sal ratus meaning "aerated salt", first used in the nineteenth century, refers to both potassium bicarbonate and sodium bicarbonate.[15]. I need only to see the dividing line I've found, around pH 8.6. Does Magnesium metal react with carbonic acid? The equilibrium arrow suggests that the concentration of the ions are equal to one another: {eq}K_a = \frac{[0.0006]^2}{[1.2]}=3*10^-7 mol/L {/eq}. Strong acids and bases dissociate well (approximately 100%) in aqueous (or water-based) solutions. The values of \(K_b\) for a number of common weak bases are given in Table \(\PageIndex{2}\). Therefore, in these equations [H+] is to be replaced by 10 pH. Try refreshing the page, or contact customer support. If we are given any one of these four quantities for an acid or a base (\(K_a\), \(pK_a\), \(K_b\), or \(pK_b\)), we can calculate the other three. So bicarb ion is. Does it change the "K" values? General base dissociation in water is represented by the equation B + H2O --> BH+ + OH-. A) Due to carbon dioxide in the air. Alte Begriffe/Zusammenhnge: Das chemische Gleichgewicht: Massenwirkungsgesetz und Formulierung des MWG aus einer Reaktionsgleichung. It's like the unconfortable situation where you have two close friends who both hate each other. Determine the value for the Kb and identify the conjugate base by writing the balanced chemical equation. Kenneth S. Johnson, Carbon dioxide hydration and dehydration kinetics in seawater, Limnol. The magnitude of the equilibrium constant for an ionization reaction can be used to determine the relative strengths of acids and bases. Acid-Base Buffers: Calculating the pH of a Buffered Solution, Psychological Research & Experimental Design, All Teacher Certification Test Prep Courses, Maram Ghadban, Elizabeth (Nikki) Wyman, Dawn Mills, Using the Ka and Kb in Chemistry Problems, Experimental Chemistry and Introduction to Matter, LeChatelier's Principle: Disruption and Re-Establishment of Equilibrium, Equilibrium Constant (K) and Reaction Quotient (Q), Using a RICE Table in Equilibrium Calculations, Solubility Equilibrium: Using a Solubility Constant (Ksp) in Calculations, The Common Ion Effect and Selective Precipitation, Acid-Base Equilibrium: Calculating the Ka or Kb of a Solution, Titration of a Strong Acid or a Strong Base, NY Regents Exam - Physics: Help and Review, NY Regents Exam - Physics: Tutoring Solution, Middle School Earth Science: Help and Review, Middle School Earth Science: Tutoring Solution, Study.com ACT® Test Prep: Practice & Study Guide, ILTS Science - Environmental Science (112): Test Practice and Study Guide, Praxis Environmental Education (0831) Prep, ILTS Science - Earth and Space Science (108): Test Practice and Study Guide, Praxis Chemistry: Content Knowledge (5245) Prep, CSET Science Subtest II Life Sciences (217): Practice Test & Study Guide, How Acid & Base Structure Affect pH & pKa Values, How to Calculate the Acid Ionization Constant, Ionization Constants of Acids & Conjugate Bases, Wildlife Corridors: Definition & Explanation, Abiotic Factors in Freshwater vs. Chemistry Stack Exchange is a question and answer site for scientists, academics, teachers, and students in the field of chemistry. For bases, this relationship is shown by the equation Kb = [BH+][OH-] / [B]. The Ka of NH 4+ is 5.6x10 -10 and the Kb of HCO 3- is 2.3x10 -8. Values of rate constants kCO2, kOH-Kw, kd, an - Generic - BNID 110417 Higher values of Ka or Kb mean higher strength. The \(pK_a\) of butyric acid at 25C is 4.83. Notice the inverse relationship between the strength of the parent acid and the strength of the conjugate base. To know the relationship between acid or base strength and the magnitude of \(K_a\), \(K_b\), \(pK_a\), and \(pK_b\). chemistry.stackexchange.com/questions/9108/, We've added a "Necessary cookies only" option to the cookie consent popup. This is the equation given by my textbook for hydrolysis of sodium carbonate: $$\ce {Na2CO3 + 2 H2O -> H2CO3 + 2 Na+ + 2 OH-}$$. Conversely, smaller values of \(pK_b\) correspond to larger base ionization constants and hence stronger bases. A conjugate acid is formed when a proton is added to a base, and a conjugate base is formed when a proton is removed from an acid. Homework questions must demonstrate some effort to understand the underlying concepts. succeed. We do, Okay, but is it H2CO3 or HCO3- that causes acidic rain? Two species that differ by only a proton constitute a conjugate acidbase pair. Thanks for contributing an answer to Chemistry Stack Exchange! This order corresponds to decreasing strength of the conjugate base or increasing values of \(pK_b\). The conjugate acidbase pairs are listed in order (from top to bottom) of increasing acid strength, which corresponds to decreasing values of \(pK_a\). In freshwater ecology, strong photosynthetic activity by freshwater plants in daylight releases gaseous oxygen into the water and at the same time produces bicarbonate ions. The Ka value is the dissociation constant of acids. Normal pH = 7.4. This constant gives information about the strength of an acid. Answered: Calculate the Kb values for the CO32- | bartleby For the oxoacid, see, "Hydrocarbonate" redirects here. This explains why the Kb equation and the Ka equation look similar. To subscribe to this RSS feed, copy and paste this URL into your RSS reader. The Ka expression is Ka = [H3O+][F-] / [HF]. Identify the general Ka and Kb expressions, Recall how to use Ka and Kb expressions to solve for an unknown. The respective proportions in comparison with the total concentration of calcium carbonate dissolved are $\alpha0$, $\alpha1$ and $\alpha2$. Was ist wichtig fr die vierte Kursarbeit? Both the Ka and Kb expressions for dissociation can be used to determine an unknown, whether it's Ka or Kb itself, the concentration of a substance, or even the pH. Asking for help, clarification, or responding to other answers. Making statements based on opinion; back them up with references or personal experience. The higher the Kb, the the stronger the base. $$\frac{\ce{[HCO3-]}}{Cs} = \ce{\frac{K1[H3O+]}{[H3O+]^2 + K1[H3O+] + K1K2}} = \alpha1$$, So we got the expression for $\alpha1$, that has a curious structure: a fraction, where the denominator is a polynomial of degree 2, and the numerator its middle term. Chemistry Stack Exchange is a question and answer site for scientists, academics, teachers, and students in the field of chemistry. {eq}[H^+] {/eq} is the molar concentration of the protons. Solving for {eq}[H^+] = 9.61*10^-3 M {/eq}. Do new devs get fired if they can't solve a certain bug? What are practical examples of simultaneous measuring of quantities? Lactic acid (\(CH_3CH(OH)CO_2H\)) is responsible for the pungent taste and smell of sour milk; it is also thought to produce soreness in fatigued muscles. Create your account. But how can I calculate $[\ce{HCO3-}]$ and $[\ce{CO3^2-}]$? It can be assumed that the amount that's been dissociated is very small. Bases, on the other hand, are molecules that accept protons (per Bronsted-Lowry) or donate an electron pair (per Lewis). The values of \(K_a\) for a number of common acids are given in Table \(\PageIndex{1}\). | 11 Styling contours by colour and by line thickness in QGIS. Accessibility StatementFor more information contact us [email protected] check out our status page at https://status.libretexts.org. It is a white solid. [1], It is manufactured by treating an aqueous solution of potassium carbonate with carbon dioxide:[1]. High values of Kc mean that the reaction is product-favored, while low values of Kc mean that the reaction is reactant-favored. Let's start by writing out the dissociation equation and Ka expression for the acid. Just as with \(pH\), \(pOH\), and pKw, we can use negative logarithms to avoid exponential notation in writing acid and base ionization constants, by defining \(pK_a\) as follows: Similarly, Equation 16.5.10, which expresses the relationship between \(K_a\) and \(K_b\), can be written in logarithmic form as follows: The values of \(pK_a\) and \(pK_b\) are given for several common acids and bases in Table 16.5.1 and Table 16.5.2, respectively, and a more extensive set of data is provided in Tables E1 and E2. Bicarbonate is easily regulated by the kidney, which . How does carbonic acid cause acid rain when $K_b$ of bicarbonate is greater than $K_a$? Hence this equilibrium also lies to the left: \[H_2O_{(l)} + NH_{3(aq)} \ce{ <<=>} NH^+_{4(aq)} + OH^-_{(aq)}\]. Solved True or False Consider the salt ammonium | Chegg.com Sodium Bicarbonate | NaHCO3 or CHNaO3 | CID 516892 - structure, chemical names, physical and chemical properties, classification, patents, literature, biological . Following this lesson, you should be able to: To unlock this lesson you must be a Study.com Member. $$K1 = \frac{\ce{[H3O+][HCO3-]}}{\ce{[H2CO3]}} \approx 4.47*10^-7 $$, Second stage: It can substitute for baking soda (sodium bicarbonate) for those with a low-sodium diet,[4] and it is an ingredient in low-sodium baking powders.[5][6]. We know that the Kb of NH3 is 1.8 * 10^-5. Calculate \(K_a\) for lactic acid and \(pK_b\) and \(K_b\) for the lactate ion. At equilibrium the concentration of protons is equal to 0.00758M. Legal. Oceanogr., 27 (5), 1982, 849-855 p.851 table 1. The Kb formula is: {eq}K_b = \frac{[B^+][OH^-]}{[BOH]} {/eq}. We would write out the dissociation of hydrochloric acid as HCl + H2O --> H3O+ + Cl-. Values of rate constants kCO2, kOH-Kw, kd, and kHCO3- and first dissociation constant of carbonic acid calculated from the rate constants. We could also have converted \(K_b\) to \(pK_b\) to obtain the same answer: \[K_a=10^{pK_a}=10^{10.73}=1.9 \times 10^{11}\]. The molar concentration of protons is equal to 0.0006M, and the molar concentration of the acid is 1.2M. Initially, the protons produced will be taken up by the conjugate base (A-^\text{-}-start . The Ka formula and the Kb formula are very similar. $$\ce{H2O + H2CO3 <=> H3O+ + HCO3-}$$ {eq}HA_(aq) + H_2O_(l) \rightleftharpoons A^-_(aq) + H^+_(aq) {/eq}. It is about twice as effective in fire suppression as sodium bicarbonate. So we are left with three unknown variables, $\ce{[H2CO3]}$, $\ce{[HCO3-]}$ and $\ce{[CO3^2+]}$. [10][11][12][13] 120CH2CO3Ka1=4.2107Ka2=5.61011NH3H2OKb=1.7105 We use dissociation constants to measure how well an acid or base dissociates. The application of the equation discussed earlier will reveal how to find Ka values. Bicarbonate (HCO3) - Lab Tests Guide [8], Potassium bicarbonate has widespread use in crops, especially for neutralizing acidic soil. I would like to evaluate carbonate and bicarbonate concentration from groundwater samples, but I only have values of total alkalinity as $\ce{CaCO3}$, $\mathrm{pH}$, and temperature. Strong acids are listed at the top left hand corner of the table and have Ka values >1 2. To solve this problem, we will need a few things: the equation for acid dissociation, the Ka expression, and our algebra skills. Ka for HC2H3O2: 1.8 x 10 -5Ka for HCO3-: 4.3 x 10 -7Using the Ka's for HC2H3O2 and HCO3, calculate the Kb's for the C2H3O2- and CO32- ions. Ka is the dissociation constant for acids. If I understood your question correctly, you have solutions where you know there is a given amount of calcium carbonate dissolved, and would like to know the distribution of this carbonate between all the species present. The equilibrium constant for this dissociation is as follows: \[K=\dfrac{[H_3O^+][A^]}{[HA]} \label{16.5.2}\].