The subscripts in the chemical formula of the compound can be used to determine the relative ion concentrations Now mL to L Start your 48-hour free trial to get access to more than 30,000 additional guides and more than 350,000 Homework Help questions answered by our experts. If it is not neutral, explain your choice by writing a balanced net ionic equation to describe its behavior in water. 2023 eNotes.com, Inc. All Rights Reserved. Contact. (C) NO_3^-. National Library of Medicine. a) Na2CO3 b) (CH3NH3)Br c) CsI. eNotes.com will help you with any book or any question. "Freezing Point Depression Example Problem." This means that over a period of about two billion years, the Colorado River carved rock from the surface by slowly dissolving it, eventually generating a spectacular series of gorges and canyons. While full chemical equations show the identities of the reactants and the products and give the stoichiometries of the reactions, they are less effective at describing what is actually occurring in solution. Rank the solutions in order of increasing electrical conductivity, knowing that the greater the number of ions in solution, the greater the conductivity. (determinant of how acidic or basic a substance is) P.S, H+ (aq.) The following equations represents hydrolysis of the given salts: {eq}\rm \hspace{4cm} Na_{2}CO_{3}~(s) + 2H_{2}O~(l) \longrightarrow 2NaOH~(aq) + H_{2}CO_{3}~(aq) What Are The Concentrations Of Oh- And H+ In A Solution Of Ba(Oh)2 NH3 + HCl also gives NH4Cl right ( 1 vote) Flag Shivani Choose the ion responsible for the acid/base character of the solution and write its acid/base reaction with water. Check image for possible answer choices, NH3+ (aq) + HNO3 (aq) --> NH3NO3 (aq) + H2O (aq) The carbonate ion being a conjugate base may form the bicarbonate ion (HCO_3) and carbonic acid (H_2CO_3) in solution Ka1 and Ka2 for carbonic acid are 4.45 x 10^(-7) a. The quantity of Cl- in a municipal water supply is determined by titrating the sample with Ag+. 1. fluoride ion, hydronium ion, and water 2. fluoride ion, hydroxide ion. Omit water from the equation because it is understood to be present. Choose an expert and meet online. Write an equation for the reaction of H2CO3 with CO3^2-. What is the concentration of the NaOH solution? Write the equation for the dissociation of carbonic acid. Suppose you prepare 0.250 M solutions of hydrobromic acid and potassium hydroxide. a) Write the molecular equation for the reaction. For example, freezing point depression occurs when either salt or alcohol are added to water. Definitions of Acids and Bases. Write An Equation That Justifiesits Basicity. {/eq} : Dissociation of {eq}\rm K_{3}PO_{4} {/eq}). mol AgNO3 = 0.050Mx 0.015 L = 7.5x10^-4 mol AgNO3 B) Mn^{3+}. Predict whether an aqueous solution of Na2CO3 would be acidic, basic, or neutral. 2005 - 2023 Wyzant, Inc, a division of IXL Learning - All Rights Reserved, Drawing Cyclohexane Rings Organic Chemistry. Calculate the moles of each constituent ion formed when 0.75 moles of {eq}K_3PO_4 chemistry All other trademarks and copyrights are the property of their respective owners. Write an equation that represents how dihydrogen phosphate ion (H_2PO_4^-) behaves as an Arrhenius acid. . Please need help with this. KPO is potassium phosphate, a water-soluble ionic salt. c) Fe, the amount of solute dissolved in a given quantity of solvent or quantity of solution, (M) 1. k3po4 dissolved in water equation - MEBW A positive or negative whole number assigned to an element in a molecule or ion on the basis of a set of formal rules: Complete the equation for the dissociation of k3po4(aq) Solubility Solubility is the property of a solid, liquid, or gaseous chemical substance called solute to dissolve in a solid, liquid, or gaseous solvent. Write the net ionic equation for the acid-base hydrolysis equilibrium that is established when calcium hypochlorite is dissolved in water. Determine whether each anion is basic or neutral. Weak = HCOOH Determine the net Bronsted acid-base equation for the reaction that occurs when aqueous solutions of HNO2 and NaOH are mixed. But it is actually ever so slightly soluble. Sleeping In Discord Calls, Net ionic equations show only the ions and other substances that change in a chemical reaction. d) Br = -1; Sn = +4 NH_4Cl. a) 1:0.015 Join Yahoo Answers and get 100 points today. When HCl (strong acid) is added to this buffer system, the extra H+ ions added to the system are consumed by the NH3 to form NH4+. How to Calculate Freezing Point Depression - ThoughtCo a) NiSO4 Write the net ionic equation for each chemical reaction. Metabolites | Free Full-Text | Biopreservative Effect of the Tunisian Be sure that math assignments completed by our experts will be error-free and done according to your instructions specified in the submitted order form. Water-soluble potassium phosphate, {eq}K_3PO_4 Include physical states. The problem is that too much limescale can impede the function of a water heater, requiring more energy to heat water to a specific temperature or even blocking water pipes into or out of the water heater, causing dysfunction. 2 HCl (aq) + Ba(OH)2 (aq) --> BaCl2(s) + 2 H2O (aq) In this instance, water acts as a base.The equation for the dissociation of acetic acid, for example, is CH 3 CO 2 H + H 2 O CH 3 CO 2 + H 3 O +.. Dissociation of bases in water. Write the net Bronsted equation and determine the equilibrium constant for the acid-base reaction that occurs when aqueous solutions of H2CO3 and KHS are mixed. When a solute is added to a solvent, its freezing point is lowered from the original value of the pure solvent. Keep in mind that when the ions separate, all the ions separate. Solved Sodium carbonate dissolved in water produces a basic - Chegg Screen capture done with Camtasia Studio 4.0. 7.5x10^-4 mol AgNO3 - 9.96x10^-4 mol AgNO3 = -2.46x10^4 mol AgNO3 One important aspect about ionic compounds that differs from molecular compounds has to do with dissolution in a liquid, such as water. To show that they are dissolved in water we can write (aq) after each. expresses the concentration of a solution as the # of moles of solute in 1 L of solution The Journal of Physical Chemistry C 2023, 127, 8, 4341-4350 (C: Physical Properties of Materials and Interfaces) Publication Date (Web): February 21, 2023. Aqueous electrolyte sodium ion. Medical search. Frequent questions Complete ionic equations show dissolved ionic solids as separated ions. Write the net ionic equation for the reaction, which makes a solution Na_2CO_3 basic. molality (m) of NaCl = moles of NaCl/kg waterFrom the periodic table, find the atomic masses of the elements:atomic mass Na = 22.99atomic mass Cl = 35.45moles of NaCl = 31.65 g x 1 mol/(22.99 + 35.45)moles of NaCl = 31.65 g x 1 mol/58.44 gmoles of NaCl = 0.542 molkg water = density x volumekg water = 0.994 g/mL x 220 mL x 1 kg/1000 gkg water = 0.219 kgmNaCl = moles of NaCl/kg watermNaCl = 0.542 mol/0.219 kgmNaCl = 2.477 mol/kg. Chemistry 60 - Lec Notes 2023 - Summary 18 Periodicity This section {/eq}. c) How many grams of iron were in the sample? Write a chemical equation to justify your choice. The (aq) shows that they are aqueous dissolved in water.The equation for K2SO4 ( Potassium sulfate and H2O sometimes isnt considered a chemical reaction since it is easy to change the K+ and SO4 2- back to K2SO4 (just let the H2O evaporate). K3PO4 has an IUPAC name of Tripotassium. {/eq}) which is a weak acid. c) O = 2-, Cr = +6 a) 0.0313 M Chemistry-Reference.com provides you with capsules on many topics in chemistry. d) sodium a) 1.75 mL Wayne Breslyn 632K subscribers 10K views 2 years ago To tell if K3PO4 (Potassium phosphate) forms an acidic, basic (alkaline), or. Write a net ionic equation for the reaction of each antac. Answer in General Chemistry for jimbo #92002 - Assignment Expert 275.0 mL x (1 L/1000 ml) = 0.275 L NH3+ + 3H+ --> NH4+ + H2O H20 + K+ --/-> KOH The equilibrium is in the other direction. The equation can further be written as, Tb =. Ziggy Twitch Girlfriend, a) O2 crcl3 soluble or insoluble how to find assumed mean of ungrouped data. d) sodium nitrate Predict qualitatively whether the salts below dissolve to give solutions that are acidic, basic or neutral. = 0.0195 g Na2S b) the net ionic equation. Latest answer posted July 17, 2012 at 2:55:17 PM. Consider only its first ionization _____ + h20 ---> ______ + ______ Classify phosphoric acid as a monop. NaHCO_3. Decomposition Of Ammonium Chloride, Match each type of compound with the ion each produces. The (aq) shows that they are aqueous dissolved in water.The equation for MgSO4 ( Magnesium sulfate and H2O sometimes isnt considered a chemical reaction since it is easy to change the Mg 2+ and SO4 2- back to MgSO4 (just let the H2O evaporate). Traditions Outfitter G2 35 Rem Review, Freezing Point Depression Example Problem. The K_a for HS^1- is 1.3 times 10^-13. d) 1:2 There are three main steps for writing the net ionic equation for K3PO4 + AgNO3 = Ag3PO4 + KNO3 (Potassium phosphate + Silver . b. name and write the formula of the ion that makes a solution basic. Is K3PO4 acidic, basic, or neutral (dissolved in water)? (a) What is the molarity of K3PO4? 4 Chapter 4 Chemistry 1303 B. Molecular and Ionic Equations Metathesis Reaction (also called "double displacement") Ions from two different reactants simply trade partners, Na2CO3 (aq) + Ba(NO3)2 (aq) BaCO3 (s) + 2 NaNO3 (aq) This was written as a molecular equation in which all reactants and products are shown as complete, neutral chemical formulas. V1 = (0.10 x 450)/3.0 are needed to prepare Write the chemical equation for the reaction of carbonic acid (H_2CO_3) with water. Express your answer as an ion. Silver nitrate, or AgNO3, mixed with distilled water is a solution. Helmenstine, Todd. See Answer. e) Pb(CH3COO)2, Classify the following compounds as soluble or insoluble in water: Mass/ molecular weight = 50 g / 110.98 g/mol = 0.450 mol So now you know there is 0.450 mol per 250 mls, you just convert to mol l-1. Salt water. 845 mL Get Started Write the ions present in a solution of K3PO4. 23.4 g Na2SO4 x (1 mol Na2SO4/142.04 g Na3SO4) = 0.165 mol Na2SO4 Most questions answered within 4 hours. When you dissolve table salt (sodium chloride, also known as NaCl) in water, are you producing a chemical change or a physical change? What is the compound name of the formula? Show the reaction with H+ as. Ksp = 1.8 1014 What Is The Solubility Of M(Oh)2 In A 0.202 M Solution Of M(No3)2 What Is The Ph Of An Aqueous Solution With [H3O+] = 41013 [] When the salt dissolves, it is not a chemical reaction, so no new substance is created. Determine the net Bronsted acid-base equation for the reaction that occurs when aqueous solutions of NaC2H3O2 and H3PO4 are mixed. Learn more about our help with Assignments: Thank you! what is thebalanced dissociation equation for KCN (s)? a) The hydrogen phosphate ion, HPO4-, is amphiprotic and can act as an acid or base. Write the ions present in a solution of k3po4k3po4 Freezing point depression is calculated using Raoult's Law and the Clausius-Clapeyron Equation to write an equation called Blagden's Law. 8.11: Ionic Equations - Chemistry LibreTexts b) hydrofluoric acid mol= M x L to some degree it reflects the positive or negative character of that atom The van 't Hoff factor, i, is a constant associated with the amount of dissociation of the solute in the solvent. b) 0.038 mol Na2SO4/0.50 M = 0.076 L How is the molarity of a 0.50 M KBr solution changed when water is added to double its volume? = 0.40 M. How many grams of Ca(OH)2 are needed to neutralize 25.0 mL of 0.100 M HNO3? Molar mass = 285.34 g/mol How many grams of solute are present in a. (water) it will dissociate (dissolve) into K+ and PO4 3- ions. Write the ions present in a solution of k3po4 | Math Materials b) the complete ionic equation, Answer Save. Alkali Salts : Alkali salts are basic salts are that. # of moles of morphine = # of moles of HCl Justify by writing out any pertinent chemical reaction that shows how it contributes to its acidity or basicity. Video \(\PageIndex{1}\): Mixing Potassium Chromate and Silver Nitrate together to initiate a precipitation reaction (Equation \(\ref{4.2.1}\)). B) The compound ammonium bromide , NH4Br is soluble in water. a_ Chloric Acid Write the formula for the hydronium ion. 20 g of K3PO4 dissolved in 350 ml water,to come up with 500 ml solution. (2021, July 1). b. HClO_3. Your physics assignments can be a real challenge, and the due date can be really close feel free to use our assistance and get the desired result. Educators go through a rigorous application process, and every answer they submit is reviewed by our in-house editorial team. Ex: A + BX --> AX + B Ag+ (aq) + Cl- (aq) --> AgCl(s) Write the net ionic equation that depicts the neutralization of the base by potassium hydrogen phthalate. your equation should show a proton transfer to form carbonic acid and a salt. a) Zn Anions containing hydrogen (for example, HCO_3^- and H_2PO_4^2-) show amphoteric behavior when reacting with other acids or bases. Instead of using the entire chemical formula of phthalate, use HP- to represent the acidic hyd. c) 23.5 mg b) Ca(NO3)2 Write the equation for the dissociation into ions when 1 mole of {eq}K_3PO_4 Alcohols all consist of one hydroxyl group attached to a hydrocarbon chain. a. HF. Most bases are weak bases, except for a select few (See image), Bases that completely ionize in water b) Oxidation number of H is usually +1 when bonded to nonmetals, and -1 when bonded to metals 2) When calcium chloride and potassium phosphate are dissolved in water they react to form aqueous potassium chloride and calcium phosphate powder. b) Zinc is reduced, and copper ion is oxidized. Only soluble metal hydroxides are considered strong bases. a) Both barium nitrate and sodium chloride precipitate Get access to this video and our entire Q&A library, What is Salt Hydrolysis? In this case, the water molecule acts as an acid and adds a proton to the base. ThoughtCo. Write out the chemical equation for the equilibrium hydrolysis reaction of the hydrogen phosphate ion for both acid. 0.02250 M x 0.04720 L = 1.1x10^-3 mol MnO4(1-) Predict the pH of the following salt solutions and report as either acidic, basic, or neutral. Use the interactive menu bar located above to get started. An example, using ammonia as the base, is H 2 O + NH 3 OH + NH 4 +. Shifted two units do, Calculate the lattice energy for the formation of MgO from Mg and O 2 a) What compound precipitates when aqueous solutions of Fe2(SO4)3 and LiOH are mixed? d) 0.325 M Write the chemical equation showing dihydrogen phosphate and hydrogen phosphate conjugate acid-base relationship. 2) Neutral and Polyatomic ions - the oxidation number of a given atom is a hypothetical charge, 1) for an atom in its elemental form, (neutral or diatomic), the oxidation number is always 0 Complete this equation for the dissociation of K3PO4(aq). Omit water b. Write the net Bronsted equation and determine the equilibrium constant for the acid-base reaction that occurs when aqueous solutions of formic acid and sodium nitrite are mixed. What are the ions present in solution K3PO4. Na2SO4(s) + aq ? Identify the acid and base. Check image, HCl + NaOH --> NaCl + H2O Express your answers as chemical formulas separated by a comma. Your comments have been successfully added. If this solution were mixed with the one pictured above for HY, what species would be present in a diagram that represents the combined solutions after any possible reaction? Check Image, The substance that recieved electrons in a redox reaction, (oxidation state) Mg(s) + Co2+ (aq) + SO4- (aq) --> Mg2+ (aq) + SO4- (Aq) + Co(s) 2 NaOH + H2SO4 --> Na2SO4 (s) + 2 H2O As important. Now he has regrets. d) 32.1 mg Anything with a solubility of less that 0.01 mol/L is generally INSOLUBLE slowly errods the structural integrity of the metal by means of Redox Reactions Is K3PO4 acidic, basic, or neutral (dissolved in water)? \[\cancel{K^{+}(aq)}+Br^{-}(aq)+Ag^{+}(aq)+\cancel{C_{2}H_{3}O_{2}^{-}(aq)}\rightarrow K^{+}(aq)+\cancel{C_{2}H_{3}O_{2}^{-}(aq)}+AgBr(s)\nonumber \], \[\cancel{Mg^{2+}(aq)}+SO_{4}^{2-}(aq)+Ba^{2+}(aq)+\cancel{2NO_{3}^{-}(aq)}\rightarrow Mg^{2+}(aq)+\cancel{2NO_{3}^{-}(aq)}+BaSo_{4}(s)\nonumber \], CaCl2(aq) + Pb(NO3)2(aq) Ca(NO3)2(aq) + PbCl2(s). Sodium carbonate dissolved in water produces a basic solution. (a) Ca(NO3)2 (aq) (b) BaSO3 (aq) (c) Fe(ClO4)2 (aq), Provide the molecular, ionic, and net ionic equations for the following species when they are introduced into the carbonate buffer system: KOH (a strong base), 1).Write a net ionic equation to show that phosphoric acid, H3PO4, behaves as an acid in water. Potassium Phosphate is an inorganic compound used as a laxative, dietary supplement and for electrolyte-replacement purposes. or In this video we will describe the equation K3PO4 + H2O and write in H2O (water) it will dissociate (dissolve) into K+ and PO4 3- ions. What is more dangerous, biohazard or radioactivity? {/eq}) and Potassium Phosphate ({eq}\rm K_{3}PO_{4} When dissolved in water, does KOH behave as an acid or a base? 0:00 / 1:15 Equation for KMnO4 + H2O (Potassium Permanganate + Water) Wayne Breslyn 623K subscribers 34K views 4 years ago In this video we will describe the equation KMnO4 + H2O and write. But with the second H+, you have that H+ trying to get away from something that will be HPO4=. Explain how the equilibrium is shifted as buffer reacts w, Write down the hydrolysis reactions for the each of the salts. That is, the two chloride ions go off on their own. mol = MxL so it would decrease if L were to increase, How many milliliters of 3.0 M H2SO4 are needed to make 450 mL of 0.10 M H2SO4, M1V1 = M2V2 Consider solutions in which 0.1 mol of each of the following compounds is dissolved in 1 L of water: Ca(NO3)2, C6H12O6, NaCH3COO, and CH3COOH. c) SCl2 Mg(s) + Co2+ (aq) --> Mg2+ (aq) + Co(s) C) Acetic acid, CH3COOH. 0.0100 M x 0.00284 L = 2.84x10^-5 mol HCl Write the ions present in a solution of k3po4 - Math Solver then HSO4 --> H+ + SO4 2-. 0.10 mol/L = moles Mconc x Vconc = Mdil x Vdil Not only do the two sodium ions go their own way, but the sulfate ion stays together as the sulfate ion. The structural formula of citric acid, a main component of citrus fruits, is (see image) c) SrCl2 (aq) + Na2SO4 (aq) --> {/eq} produces Potassium Hydroxide (KOH) which is a strong base and Phosphoric acid ({eq}\rm H_{3}PO_{4} Write an equation for the neutralization of vinegar with baking soda. Explain this statement with an equation showing the reaction between the acid and potassium hydroxide. 1. The solute must be non-volatile. CaCl2 (aq) + Na2CO3 (aq) --> CaCO3 (s) + 2 NaCl (aq) Consider the following chemical equation to answer the questions below. Get a free answer to a quick problem. If you were to draw diagrams representing aqueous solutions of Potassium has positive charge (+1), compound has neutral charge. a) (NH4)2S \\ a)\ KBr\\ b)\ NaNO_2\\ c)\ Al(NO_3, Would a solution of each of the following salts be acidic, basic, or neutral? I. Hydrogen ion II. The reason is that freezing point occurs when the vapor pressure of the liquid and solid solvent are at equilibrium. Which ion ( Z n 2 + or S O 2 4 ) causing the acidity or basicity? b) Write the balanced chemical equation for the reaction, BaCl2 + K2SO4 -> BaSO4 (s) + 2 KCl c) the net ionic equation. Todd Helmenstine is a science writer and illustrator who has taught physics and math at the college level. (8.1x10^-3 g/0.01 g) = 81% The solubility of Na 2 CO 3 and K 3 PO 4 has been measured in near- and supercritical water.. This is more representative of what is occurring in the solution. We usually think of rock as insoluble. {eq}\rm \hspace{4cm} K_{3}PO_{4}~(s) + 3H_{2}O~(l) \longrightarrow 3KOH~(aq) + H_{3}PO_{4}~(aq) = 0.0025 mol HNO3 We consider \(\ce{NaCl}\) soluble but \(\ce{AgCl}\) insoluble. mol of HCl = How to find how many moles are in an ion? | Socratic Na_2CO_3. Solving mathematical problems can be challenging and rewarding. For example, you can dissolve a maximum of 36.0 g of NaCl in 100 g of water at room temperature, but you can dissolve only 0.00019 g of AgCl in 100 g of water. If aqueous hydrofluoric acid is reacted with sodium hydroxide, which of the following substances are in the net ionic equation? The dissociation equation when the compound is dissolved in water is as follows: {eq}\rm K_3PO_4(s) \rightarrow 3K^+(aq) + PO_4^{3-}(aq){/eq}. By analogy to examples given in the text, predict what gas forms when Na2SO3 (a) reacts with HCl (aq). what is the rule for figuring this out? 0.500 M x 0.0457 L = 0.0229 mol H2SO4 Will a precipitate form when solutions of Ba(NO3)2 and KOH are mixed? A) Sr^{2+}. ex: c) 1:1 4) The sum of oxidation numbers in all neutral compounds is 0. (B) I^-. Question: Sodium Carbonate Dissolved In Water Produces A Basic Solution.Water-soluble Potassium Phosphate, K3PO4,also Produces A Basic Solution. 2 Al3+ (aq) + 6 H+ (aq) + 6 Br- (aq) --> 2 Al3+ (aq) + 3 H2 (g) + 6 Br - (aq) Write the net acid-base reaction that occurs when dissolved NaC2H3O2 reacts with water. Replace immutable groups in compounds to And by the time the third H+ leaves, there will be a full PO4 3- pulling it back. (First show the reaction with H+ (aq) as a product and then with the hydronium ion.) 0.00202 mol Ag+ x (1 mol Cl-/1 mol Ag+ ) x (35.45 g Cl-/1 mol cl-) = 0.0072 g Cl- These measurements at 30 MPa and 320500 C complete a gap in the literature.. To calculate the moles of each ion formed, we multiply the amount of {eq}\rm K_3PO_4{/eq} by its mole ratio with each ion: {eq}\rm 0.75\:mol_{K_3PO_4} \times \dfrac{3\:mol_{K^+}}{1\:mol_{K_3PO_4}}= 2.25\:mol_{K^+} This high solubility is caused by the short hydrocarbon chain and the presence of a hydroxyl group. e) all three solutions have the same electrical conductivity. In this video we will describe the equation K3PO4 + H2O and write in H2O (water) it will dissociate (dissolve) into K+ and PO4 3- ions. A. Would hcl and nacl make a buffer? Explained by Sharing Culture Funniest Hinge Answers, The equation is already balanced. Answer: E. A sample of an iron ore is dissolved in acid, and the iron is converted to Fe2+. L = mol/M It dissociates in water. 0.015 mol K2CO3/L x (1 mol CO3 2-/1 mol K2CO3) = 0.015 M CO3 2- 3H+ (aq) + 3 OH- (aq) --> 3 H2O (l). Ca+ (aq) + CO3 2- (aq) --> CaCO3 (s), What happens when you mix an aqueous solution of sodium nitrate with an aqueous solution of barium chloride? Explain how gene regulation makes cell specialization possible. They become dissociated ions in their own right. Equation for K3PO4 + H2O (Potassium phosphate + Water) Similarly, a compound consists of a number of ions or atoms. To tell if K3PO4 (Potassium phosphate) forms an acidic, basic (alkaline), or neutral solution we can use these three simple rules along with the neutralization reaction that formed K3PO4 .First we need to figure out the acid and base that were neutralized to form Potassium phosphate. Explain your choice by showing the reaction of the acid/base with water. a. 1) Monoatomic ions - oxidation number is the same as the charge We can find the net ionic equation for a given reaction using the following steps: Write the balanced molecular equation for the reaction, including the state of each substance. b) 3H+ + PO3- + 3K+ + 3 OH- --> 3K+ + PO3 - + 3H2O (l) Write the formula of the conjugate base for acid H2CO3. Write the ionic equation that shows why the solution is acidic or basic. According to the soubility table, Ba2+ is not very soluble and therefore makes the precipitate. Freezing point depression calculations apply to dilute solutions. A reaction in which an acid and a base react in stoichiometrically equivalent amounts; the neutralization reaction between and a metal hydroxide produces water and salt, Any ionic compound whose cation comes from a base and whose anion comes from an acid.
k3po4 dissolved in water equation