Alief ISD Chemistry STAAR Review. Reporting Category 5: Solutions The Importance of Water

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1 Alief ISD Chemistry STAAR Review C. 10.A Describe the unique role of water in chemical and biological systems. Reporting Category 5: Solutions The Importance of Water Factors that contribute to water s unique properties: 1. Water is a polar molecule 2. Hydrogen bonding Polar molecule: a covalent molecule that has a slightly negative end and a slightly positive end due to unequal electron sharing. Water molecules are polar. Polar molecules are attracted to one another---the negative end of one polar molecule is attracted to the positive end of another polar molecule. Hydrogen atoms in one water molecule form attractions to the oxygen atom of other water molecules. The strong intermolecular attractions between water molecules lead to the formation of hydrogen bonds. Each water molecule forms up to two hydrogen bonds with other molecules. These hydrogen bonds contribute to many of the unique properties of water such as high surface tension, high specific heat, adhesion, and cohesion. Hydrogen bonding Non-polar molecule: a covalent molecule that has equal sharing of electrons, ex. N 2, therefore no charges are formed.

2 What role does water play in chemical systems? 1. Water as a Solvent: Because water is both strongly polar and forms hydrogen bonds, polar substances and ionic substances dissolve in water. An aqueous solution is water that contains dissolved substances. 2. High Specific Heat: Because it is nonreactive, water is a useful medium for many chemical reactions. Water has high specific heat, which allows it to resist changes in temperature. As a result, it has an unusually low freezing point and high boiling point. As water is heated, much of the energy is absorbed by the bonds within and between each molecule. A gram of water absorbs 2270 joules before it evaporates. Because water absorbs energy with only minimal changes in temperature or state, it is useful for cooling other systems, like nuclear reactors. 3. Neutrality: Water is also unusual in its neutrality. Water dissociates into hydrogen ions (H + ) and hydroxide ions (OH - ). Water is a neutral substance because it produces hydrogen ions and hydroxide ions at the same rate. 4. Density of Solid Water: The solid phase for most substances is denser than the liquid phase. That is not the case with water. When water freezes, the hydrogen atoms and oxygen atoms align themselves into a crystal pattern that has more space between each molecule than in liquid. This expansion of molecules cause solid water (ice) to be less dense than liquid water. Atomic Pattern of Liquid Water Atomic Pattern of Ice What role does water play in biological systems? Water is an important part of every living thing. It is an excellent solvent that can transport nutrients and wastes. Hydrogen bonding between water molecules gives water a property called cohesion--- the attraction between molecules of the same substance. Drops of water form on substances, such as table tops, because surface water molecules are drawn inward due to cohesion.

3 Surface water molecules are hydrogen bonded only on the inside of the drop. This inward force is called surface tension. Surface tension, a property of water that makes its boundary behave something like stretched Saran Wrap for small things. When water comes in contact with certain substances that attract water, called hydrophilic substances, water will rise through adhesion---an attraction between molecules of a different substance. See diagram below to remember the difference between cohesion and adhesion. Water not only sticks to itself (cohesion), it sticks to the wood as you can see by looking at the arrows in the picture above. This is called adhesion because the attraction is to a different substance. Adhesion leads to water traveling from a plant s roots to its stems and leaves. Water also helps regulate the temperature of living organisms because it has a high heat capacity. It resists rapid change in temperature and absorbs a great deal of heat when it evaporates.

4 Bodies of water also resist changes in temperature, which affects climate. Finally because ice is less dense than liquid water, ice floats on bodies of water. The ice insulates the liquid water below it from the cold air. This usually prevents bodies of water from freezing completely, which allows fish and other aquatic life to survive winters. C.10.B Develop and use general rules regarding solubility through investigations with aqueous solutions Solubility Rules REFER to the STAAR Chemistry Reference Materials on Solubility of Common Ionic Compounds in Water when figuring out if a compound is soluble or insoluble. Vocabulary words you must know: 1. Solubility: The solubility of a substance is a measure of the amount of solute that can dissolve in a given quantity of a solvent at a specified temperature and pressure. Solubility of solids is often expressed in grams of solute per 100 g of solvent (g/100 g H 2 O). Example: Solubility of K 2 Cr 2 O 7 at 25 o C is about 15 g/100ml of H 2 O. 2. Solution: A mixture blended so that properties are the same throughout; one substance, the solute, dissolves in another substance called the solvent. Therefore, the solvent is doing the dissolving. Solvents are often a liquid, but the solutes and solvents can be solid, liquid, or gas. Adding a solute(s) to a liquid solution elevates (increases) the solutions boiling point and depresses (decreases) the solution s freezing point.

5 3. Aqueous solution (aq): A solution in which the solvent is liquid water. 4. Soluble: Substance dissolved in solution. Example-sugar is soluble in water. 5. Insoluble: Substance does not dissolve in solution. Example: oil is insoluble in water. 6. Precipitate: Solid formed from two aqueous solutions. The symbol (s) is used to show that a substance is a solid when writing a chemical equation (g) is a gas.(l) is a liquid.(aq) dissolved in water. 7. Dissociation: Occurs when compound dissolves and forms ions. Cation (+) Anion (-) HCl dissociates to form H + and Cl -, but C 6 H 12 O 6 does not.

6 8. General solubility rules: Like dissolves like means that nonpolar compounds dissolve best in nonpolar solvents, whereas polar and ionic compounds (like salt) dissolve best in polar solvents (like water). Example: Oil (non-polar) is not soluble in water (polar). Using Solubility Rules: Water solubility rules for ions: Guidelines to help predict which ionic compounds are soluble based on the cation and sometimes the anion depending on chart that you use. REFER to the STAAR Chemistry Reference Materials on Solubility of Common Ionic Compounds in Water when figuring out if a compound is soluble or insoluble. Example Problem 1: Is Na 2 CrO 4 soluble in water? Yes, Na + is an alkali metal cation and looking at the STAAR chart the anion CrO 4 2- is insoluble except when combined with NH 4 + and the alkali metal cations. Example Problem 2: Is BaSO4 soluble in water? No, Ba 2+ is an alkaline earth metal, and the rule for the SO 4 2- anion is that the salt is insoluble if cation is Ba 2+, Sr 2+, Pb 2+ and Hg Example Problem 3: Which product in the equation below is a precipitate? AlCl 3 (aq) + K 3 PO 4 (aq) 3KCl(?) + AlPO 4 (?) The product AlPO 4 (s) is the precipitate because according to the STAAR Solubility Chart the anion PO 4 3- is insoluble except when combined with NH 4 + and the alkali metal cations.since Al is not an alkali metal then AlPO 4 is insoluble or the precipitate in solution. KCl(aq) is soluble in solution because the anion Cl - is soluble except when combined with Ag +, Pb 2+, and Hg 2 2+.

7 How to write a balanced net ionic equation: A net ionic equation shows only those particles involved in the reaction and is balanced with respect to both mass and charge. Consider the equation for the reaction of potassium chloride with silver nitrate. EXAMPLE PROBLEM 1: Molecular Equation: KCl(aq) + AgNO 3 (aq) AgCl(s) + KNO 3 (aq) Complete Ionic Equation: (Remember: any ionic compound dissolved in water will be present as the separated ions. K + (aq) + Cl - (aq) + Ag + (aq) + NO 3 - (aq) AgCl(s) + K + (aq) + NO 3 - (aq) Spectator Spectator Solid, Spectator Spectator ion ion not ion ion written as separate ions The ions that do not participate directly in the reaction are called spectator ions. You will see them on both sides of the equation. Cross the spectator ions out to write the net ionic equation. This equation includes only those solution components directly involved in forming the precipitate (solid). Net ionic equation: This equation includes only those solution components directly involved in forming the precipitate (solid). Cl - (aq) + Ag + (aq) AgCl(s) EXAMPLE PROBLEM 2: Write the molecular equation, the complete ionic equation, and the net ionic equation for the following: 3KOH(aq) + Fe(NO 3 ) 3 (aq) Fe(OH) 3 (s) + 3KNO 3 (aq) Molecular equation: 3KOH(aq) + Fe(NO 3 ) 3 (aq) Fe(OH) 3 (s) + 3KNO 3 (aq) Complete Ionic equation: Remember: The precipitate does not break down into ions. 3K + (aq) + 3OH - (aq) + Fe 3+ (aq) + 3NO 3 - (aq) Fe(OH) 3 (s) + 3K + (aq) + 3NO 3 - (aq) Ionic equation: This equation does not show the spectator ions; only the ions that directly made the precipitate: 3OH - (aq) + Fe 3+ (aq) Fe(OH) 3 (s)

8 C.10.C Calculate the concentration of solutions in units of molarity Calculations Involving Molarity How to describe the concentration of a solution: A solution that contains a relatively small amount of solute is a dilute solution. By contrast, a solution that contains a large amount of solute is a concentrated solution. However, dilute and concentrated are relative terms and not precise regarding the amount of solute involved. Think of orange juice. Many of you probably buy it in this form: This is concentrated orange juice. To make it you need to add it to a pitcher with water. The more water you add the weaker or more dilute the solution will be. You will have more OJ to drink but it will be very weak. If you add just a little bit of water, the OJ will be much stronger and tastier but there will be less of it to go around. To express this idea in Chemistry class, we use the concept of molarity. One of the most useful ways to describe the concentration of a solution is its molarity, also called its molar concentration. The molarity (M) of a solution is the number of moles of solute per liter of solution. For example, a 1M, or 1-molar, solution of copper sulfate (CuSO 4 ) has one mole (mol) of copper sulfate for each liter (L) of the solution. How to calculate the molarity of a solution: You can calculate molarity by dividing the amount of solute in moles by the volume of the solution in liter. Molarity (M) = moles of solute liters of solution EXAMPLE PROBLEM 1: What is the molarity of the solution if 0.25 moles of sodium sulfate (Na 2 SO 4 ) is dissolved in 1.5 L solution? Molarity (M) = moles of solute liters of solution Solution: 0.25 mol Na 2 SO 4 = 0.17 mol Na 2 SO 4 /L = 0.17 M Na 2 SO L solution

9 EXAMPLE PROBLEM 2: If you had a 2 M solution of glucose (C 6 H 12 O 6 ), how many liters of the solution would contain 3 moles glucose (C 6 H 12 O 6 )? Solution: Molarity (M) = moles of solute liters of solution Solve for liters of solution: Liters of solution = moles of solute Molarity (M) Liters of solution = 3 mol C 6 H 12 O 6 = 1.5 L 2 mol C 6 H 12 O 6 /L EXAMPLE PROBLEM 3: In many problems, the mass of solute is given instead of the number of moles. To solve this type of problem, convert grams of solute to moles of solute. Calculate the molarity of L of solution that contains 110 g sodium chloride (NaCl). Solution: First, you must find the moles of solute by converting grams of solute to moles of solute. 110 g NaCl x 1 mol NaCl = 1.9 mol NaCl g NaCl Now, solve for the molarity of NaCl. Molarity NaCl = 1.9 mol NaCl L = 3.7M NaCl C.10.D Use molarity to calculate the dilutions of solutions Calculating Dilutions Using molarity to calculate the dilutions of solutions: Diluting a solution reduces the number of moles of solute per unit volume, but the total number of moles in solution does not change. This concept can be expressed with the following equation: Moles of solute before dilution = Moles of solute after dilution Remember the definition of molarity and how it can be rearranged to solve for moles of solute: Molarity (M) = moles of solute liters of solution (V)

10 For instance, you might start with a small amount of a concentrated solution and dilute it with water. The final solution will have a larger volume but a lower concentration, and the moles of solute present will be the same after as before the dilution. This relationship can be expressed by the following formula, which states that the product of the molarity and volume of the first solution (m 1 x V 1 ), is equal to the product of the molarity and volume of the second solution (m 2 x V 2 ). Moles of solute = M 1 x V 1 = M 2 x V 2 Suppose 1.5 moles of sulfuric acid (H 2 SO 4 ) are dissolved in 0.10 L of solution. You would calculate the molarity of the solution as follows: 1.5 mol H 2 SO 4 = 15 mol H 2 SO 4 /L = 15M H 2 SO L solutions No matter how much the solution is diluted, the amount of H 2 SO 4 in the solution will still be 1.5 moles. As the sulfuric acid solution is diluted, its volume increases and its concentration decreases proportionately. EXAMPLE PROBLEM 1: What volume of 0.5 M NaOH is needed to make a M in 2 L solution? The relationship M 1 x V 1 = M 2 x V 2 can be used to find the original volume. M 1 =.5 M M 2 = M V 1 =? V 2 = 2 L Solve for V 1 : Make sure to convert ml to L before using the formula anytime the volume is given in ml.. V 1 = M 2 x V 2 = M x 2 L = 0.3 L M M

11 C.10.E Distinguish between types of solutions such as electrolytes and nonelectrolytes and unsaturated, saturated, and supersaturated solutions. Solution Electrolyte Types of Solutions Description Contains ions; conducts electricity Strong electrolyte: completely dissolves and dissociates Weak electrolyte: Partially dissolves and dissociates Nonelectrolyte Does not contain ions; does not conduct electricity Nonelectrolyte: No dissociation, all molecules in solution Unsaturated Able to dissolve more solute; not yet saturated If you add one teaspoon of sugar to iced tea, you've got an unsaturated solution.

12 Saturated Contains maximum solute amount that can dissolve at that temperature (at equilibrium) If you keep adding sugar to iced tea, you eventually get to the point where the rest of the sugar just sinks to the bottom. When this happens, it means that the solution is saturated, because no more sugar could dissolve. Supersaturated Contains more solute than saturated; unstable; made by cooling or evaporating solvent from saturated solution This means that MORE solute has dissolved than is possible. Solubility Graph Defining Unsaturated, Saturated, and Supersaturated Solutions Definitions- On the line=saturated (full can not hold anymore solute) Above the line= supersaturated (holding more solute than it should, unstable condition) Below the line=unsaturated (can hold more solute)

13 C.10.F Investigate factors that influence solubilities and rates of dissolution such as temperature, agitation, and surface area. Rate of dissolution: Measure of how quickly a solute dissolves. Factor Factors Influencing Solubility Effect on Solubility Effect on Rate of Dissolution Temperature Solubility (usually) Rate of dissolution Agitation No effect Rate of dissolution Surface Tension No effect Rate of dissolution Common ion effect: Salt s solubility decreases if a common ion is present. How does pressure influence solubilities and rates of dissolution? Pressure does not have a significant effect on the solubilities and rates of dissolution for most solutions, except for solutions of dissolved gases. As pressure increases, the solubility of a gas increases proportionately. At higher pressures, there are more interactions between solute particles and the solvent, and more solute-solvent interactions lead to more dissolution. Solubility Graph of Gases How does increasing temperature affect the solubility of gases?

14 C.10.G Define acids and bases and distinguish between Arrhenius and Bronsted-Lowry definitions and predict products in acid-base reactions that form water. Acids and Bases Arrhenius definition of an acid: The Arrhenius definition was the first one proposed for acids and bases. An Arrhenius acid is any substance that produces hydrogen ions (H + ) in water. For example, when hydrochloric acid (HCl) is dissolved in water, it ionizes into hydrogen and chloride ions. HCl(aq) H + (aq) + Cl - (aq) Hydrochloric acid Hydrogen ion Chloride ion Remember: Acidic aqueous solutions have [H + ] > [OH - ] and turn blue litmus paper red. Arrhenius definition of a base: An Arrhenius base is any substance that produces hydroxide ions (OH - ) when it dissolves in water. For example, when calcium hydroxide, Ca(OH) 2, dissolves in water, it ionizes into calcium and hydroxide ions. Ca(OH) 2 (aq) Ca 2+ (aq) + 2OH - (aq) Calcium hydroxide Calcium ion Hydroxide ion Remember: Basic aqueous solutions have [OH - ] > [H + ] and turns red litmus paper blue. BrØnsted-Lowry definition of an acid: Not all acid-base reactions take place in aqueous solutions, so hydroxide ions are not present in every reaction between an acid and a base. BrØnsted and Lowry resolved this by defining acids and bases according to how protons are exchanged. A hydrogen ion, which is a hydrogen atom that has lost its only electron, is a proton. The BrØnsted-Lowry definition of acids and bases regards every reaction between an acid and a base as a transfer of a proton. The BrØnsted-Lowry acid, then, is any substance that donates a proton in a reaction, whether or not this takes place in a aqueous solution. For example, in a reversible reaction of ammonium (NH 4 + ) and ammonia (NH 3 ), ammonium reacts with hydroxide and donates a proton to form ammonia. NH 4 + (aq) + OH - (aq) NH 3 (aq) + H 2 O(l) Ammonium ion Hydroxide ion Ammonia Water BrØnsted-Lowry definition of a base: A BrØnsted-Lowry base is any substance that accepts a proton in a reaction. For example, consider the reversible reaction below. When ammonia (NH 3 ) reacts with water, ammonia accepts a proton to form ammonium (NH 4 + ). NH 3 (aq) + H 2 O(aq) NH 4 + (aq) + OH - (aq) Ammonia Water Ammonium ion Hydroxide ion You ll notice that while ammonia, the base, accepts a proton, water donates a proton. The water in this reaction, then, serves as an acid. In any reaction in which a proton is exchanged, the substance that accepts the proton is the base, while the substance that donates the proton is the acid.

15 Theory Acid Definition Base Definition Arrhenius Adds H3O+ ions to Adds OH- ions to solution solution BrØnsted-Lowry Proton donor Proton acceptor Predicting other products in acid-base reactions that form water: When acids and bases react, the reaction usually forms water and always forms a salt. A salt is any substance that is formed from a positive and a negative ion. Consider the reaction of sodium hydroxide (NaOH) and hydrochloric acid (HCl) shown in the equation below. When the acid loses a proton and the base provides a hydroxide ion that accepts a proton, the product is water. The sodium (Na + ) and the chloride (Cl - ) ions remain in solution as a dissolved salt, sodium chloride, NaCl(aq). This is a double replacement reaction: NaOH + HCl Na + Cl - + H 2 O base + acid salt + water C.10.H Understand and differentiate among acid-base reactions, precipitation reactions, and oxidation-reduction reactions. Types of Reaction Three important types of reactions are acid-base reactions, precipitation reactions, and oxidation-reduction reactions. These reactions commonly take place in aqueous solutions. Reaction Acid-base Description and Example Double replacement reaction; most reactions are: acid + base salt + water HCl + LiOH LiCl + H 2 O Precipitation Occurs when two aqueous solutions react and produce a solid precipitate; (s) indicates solid but if precipitate is not identified with a (s) then you can use solubility rules to predict the precipitate formed. NaCl(aq) + AgNO 3 (aq) NaNO 3 (aq) + AgCl(s) Oxidation-reduction (redox) An electron(s) from one reactant (reducing agent) is given to the other reactant (oxidizing agent); changes some oxidation numbers in the reactants. Fe + 2HCl FeCl 2 + H 2 Oxidation number of Fe changes from 0 in reactant (elemental) to +2 in ionic compound FeCl 2. H changes from +1 in reactant (HCl) to 0 in H 2. Fe is oxidized by H +, and H + is reduced by Fe. Half reactions: Fe Fe e- and 2H + + 2e- H 2

16 C.10.I Define ph and use the hydrogen or hydroxide ion concentrations to calculate the ph of a solution ph of a Solution What is ph? The strength of an acid depends on the concentration of hydrogen ion (H + ) in a solution, which can be expressed in terms of molarity. For example, the concentration of hydrogen ions in water is 1.0 x 10-7 M. This means that for each liter of water, there is mole of hydrogen ions. A much easier way to express the strength of an acid is by its ph, which is the negative logarithm of the hydrogen-ion concentration. ph = log[h + ] The ph of water is the negative of the log of 1.0 x 10-7 M, which is 7. Water has an equal amount of hydrogen ions and hydroxide ions, so it is considered neutral. Solutions with a ph lower than 7 are considered acidic, and solutions with a ph higher than 7 are considered basic. Each change of a whole number in ph represents a difference of a factor of 10 in the concentration of hydrogen ions. How is the hydrogen ion concentration used to calculate the ph of a solution? Consider an aqueous solution with a hydrogen ion (H + ) concentration of 1.0 x 10-5 M. The ph is calculated using the negative of the log of hydrogen ion concentration. ph = log (1.0 x 10-5 ) = ( 5) = 5 The hydrogen ion concentration of a solution can also be determined from its ph through a reverse of the calculation. The molar concentration of any substance is described using brackets, such as [H + ]. [H + ] = antilog ( ph) (Note: Sometimes the antilog is referred to as the inverse of the log or as log -1. On some calculators, the button for this function is labeled 10 x. ) For example, to find the hydrogen ion concentration of a solution with a ph of 11, you can calculate the antilog of -11. [H + ] = antilog (-11) = 1.0 X M Here is how you could calculate the ph of a solution with a hydrogen ion concentration of 6.3 x 10-4 M ph = log(6.3 x 10-4 ) = ( 3.3) = 3.2 How is the hydroxide ion concentration used to calculate the ph of a solution? The concentration of hydroxide ions (OH) is closely related to the ph of a solution. Recall that as water molecules disassociate, equal amounts of hydroxide ions and hydrogen ions are formed. H 2 0(l) H + (aq) + OH - (aq) Hydrogen ion Hydroxide ion

17 For all aqueous solutions, this self-ionization equilibrium is occurring, with [H + ] [OH - ] = The poh, or relative concentration of hydroxide ions, can be calculated similar to the way in which ph is calculated. poh = log[oh - ] So, taking the log of the equilibrium expression, one can derive this relationship: ph + poh = 14 This is why, in water, the ph and the poh are both 7. If an acid is added to the water, the concentration of hydrogen ions increases, lowering the ph. As the hydrogen ion concentration increases, the hydroxide concentration decreases. But the sum of the ph and the poh is always 14. On the basis of this relationship, you can calculate the poh of a solution as long as you know its ph. The hydroxide concentration can be used to find ph based on the same relationship. For example, if a solution has a hydroxide ion concentration of 1.3 x 10-10, then you can calculate the poh and then find the ph. Therefore, ph = = 4.1 poh = -log(1.3 x ) = 9.9 Alternatively, if you know the poh of a solution, then you can calculate the hydrogen ion concentration. Consider a solution with a poh of 4. How would you calculate the concentration of hydrogen ions of the solution? Use this equation to find ph: ph + poh = 14 Substitute all know variables: ph + 4 = 14 Solve for ph: ph = 14-4 = 10 The ph is 10 so the concentration of hydrogen ions is 1.0 x C.10.J Distinguish between degrees of dissociation for strong and weak acids and bases. Degrees of Dissociation for Acids and Bases To what degree do strong acids and strong bases dissociate? In general, strong acids and strong bases dissociate, or ionize, completely in aqueous solution. In other words, almost 100 percent of a strong acid or strong base interacts with water and ionizes. A strong dissociation is described using one arrow pointing to the right, as shown. HA(aq) H + (aq) + A - (aq) If a given number of moles of a strong acid, represented as HA, is added to a solution, then that same amount of its dissociated ions will be in the solution. The typical reaction of an acid in aqueous solution reacting with water can be written as HA(aq) + H 2 O(l) H 3 O + (aq) + A - (aq)

18 Strong bases generally dissociate into cations and hydroxide ions in water. For example, consider the dissociation of sodium hydroxide (NaOH). NaOH(aq) Na + (aq) + OH - (aq) To what degree do weak acids and weak bases dissociate? Weak acids and weak bases ionize only slightly in aqueous solution. This weaker dissociation can be expressed using arrows pointing in both directions. The arrows indicate that after a certain amount of the weak acid or base dissociates, the reverse reaction occurs at an equal rate. HA(aq) H+(aq) + A - (aq) If a given number of moles of a weak acid, represented as HA are added to water, then nearly that same amount of the weak acid will remain in the solution. Only a very small portion of the molecules will dissociate, representing a small fraction of the entire solution. The same is true for a weak base; only a small fraction of the molecules will dissociate. How can you distinguish between the degrees of dissociation for weak acids and bases? The degree of dissociation of a weak acid in water is represented by the acid dissociation constant (K a ). The degree of dissociation of a weak base in water is represented by the base dissociation constant (K b ). Both are calculated using the equilibrium concentrations of the acid or base, dividing the product of the concentration of the dissociated form of an acid by the concentration of the undissociated form. For example: HC 2 H 3 O 2 H C 2 H 3 O 2 Ka = [H + ][ C 2 H 3 O 2 - ] [HC 2 H 3 O 2 ] The higher the K value, the greater dissociation (strength). Ionization constant of water, K w : water can act as a weak acid or as a weak base in solution; at 25 o C: K w = [H + ][OH - ] = 1.00 x (mol/l) 2 Solve: An aqueous solution contains several solutes. What is the ph if [OH - ] = 8 x 10-5 M? K w = [H + ][OH - ] First plug in all variables that is given and solve for [H + ]. Remember the Kw for water is a constant that equals 1.00 x (mol/l) x (mol/l) 2 = [H + ] [8 x 10-5 M] 1.00 x (mol/l) 2 = [H + ] 8 x 10-5 M So, [H + ] = 1.25 x 10-10M, ph = -log[h + ] = 9.9

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