Anions containing hydrogen (for example, HCO3- and H2PO42-) show amphoteric behavior when reacting with other acids or bases. Write equations illustrating the amphoterism of these anions.
> In each of the following chemical equations, identify the conjugate acid–base pairs. a. CH3NH2 + H2O ⇌ CH3NH3+ + OH- b. CH3COOH + NH3 ⇌ CH3COO- + NH4+ c. HF + NH3 ⇌ F- + NH4+
> Suppose that 27.34 mL of standard 0.1021 M NaOH is required to neutralize 25.00 mL of an unknown H2SO4 solution. Calculate the molarity and the normality of the unknown solution.
> When hydrochloric acid, HCl, is added dropwise to a buffered solution, the component of the buffer consumes the added hydrogen ion.
> When sodium hydroxide, NaOH, is added dropwise to a buffered solution, the component of the buffer consumes the added hydroxide ion.
> Calculate the [H+] in each of the following solutions, and indicate whether the solution is acidic, basic, or neutral. a. [OH-] = 7.86 * 10-4 M b. [OH-] = 5.44 * 10-2 M c. [OH-] = 3.19 * 10-3 M d. [OH-] = 2.51 * 10-9 M
> How many milliliters of 0.50 N NaOH are required to neutralize exactly 15.0 mL of 0.35 N H2SO4?
> A buffered solution is one that resists a change in when either a strong acid or a strong base is added to it.
> A solution of phosphoric acid, H3PO4, is found to contain 35.2 g of H3PO4 per liter of solution. Calculate the molarity and normality of the solution.
> Calculate the normality of each of the following solutions. a. 0.134 M NaOH b. 0.00521 M Ca(OH)2 c. 4.42 M H3PO4
> Calculate the normality of each of the following solutions. a. 0.250 M HCl b. 0.105 M H2SO4 c. 5.3 * 10-2 M H3PO4
> The ion-product constant for water, Kw, has the value at 25 °C.
> For each of the following solutions, calculate the normality. a. 25.2 mL of 0.105 M HCl diluted with water to a total volume of 75.3 mL b. 0.253 M H3PO4 c. 0.00103 M Ca(OH)2
> How many equivalents of hydroxide ion are needed to react with 1.53 equivalents of hydrogen ion? How did you know this when no balanced chemical equation was provided for the reaction?
> An acid such as HCl that strongly conducts an electric current when dissolved in water is said to be a(n) acid.
> A solution that contains 1 equivalent of acid or base per liter is said to be a solution.
> What is a standard solution? Describe the steps involved in preparing a standard solution.
> One equivalent of an acid is the amount of the acid required to provide .
> According to the Brønsted–Lowry model, a base is a species that protons.
> According to Arrhenius, bases are species that produce ions in aqueous solution.
> The total acidity in water samples can be determined by neutralization with standard sodium hydroxide solution. What is the total concentration of hydrogen ion, H+, present in a water sample if 100. mL of the sample requires 7.2 mL of 2.5 * 10-3 M NaOH t
> Is it possible for a solution to have [H+] = 0.002 M and [OH-] = 5.2 * 10-6 M at 25 °C? Explain.
> What volume of a 0.500 M NaOH solution would be required to neutralize 40.0 mL of a 0.400 M H2SO4 solution?
> What volume of 0.502 M NaOH solution would be required to neutralize 27.2 mL of 0.491 M HNO3 solution?
> Of the following conditions, which indicate a basic solution? a. pOH = 12.53 b. pH = 3.64 c. pOH < [H1] d. [OH-] > 1.0 * 10-7 M
> Of the following conditions, which indicate an acidic solution? a. pH = 8.95 b. [H+] < 1.0 * 10-7 M c. pOH = 3.46 d. [OH-] = 7.11 * 10-10 M
> Write an equation showing how HCl(g) behaves as an Arrhenius acid when dissolved in water. Write an equation showing how NaOH(s) behaves as an Arrhenius base when dissolved in water.
> What happens to the hydroxide ion concentration in aqueous solutions when we increase the hydrogen ion concentration by adding an acid? What happens to the hydrogen ion concentration in aqueous solutions when we increase the hydroxide ion concentration b
> According to the Brønsted-Lowry model, an acid is a “proton donor” and a base is a “proton acceptor.” Explain.
> Write a chemical equation showing how each of the following species can behave as indicated when dissolved in water. a. O2- as a base b. NH3 as a base c. HSO4- as an acid d. HNO- as an acid
> Generally only the carbonates of the Group 1 elements and the ammonium ion are soluble in water; most other carbonates are insoluble. How many milliliters of 0.125 M sodium carbonate solution would be needed to precipitate the calcium ion from 37.2 mL of
> Write a chemical equation showing how each of the following species can behave as indicated when dissolved in water. a. HSO3- as an acid b. CO32- as a base c. H2PO4- as an acid d. C2H3O2- as a base
> During a summer research internship, you are asked to do lab work and prepare solutions for experiments to be run on samples that will come in from the field. You need to prepare a 0.300 M NaOH solution but only have 6.00 M NaOH on the shelf. What volume
> How much water must be added to 500. mL of 0.200 M HCl to produce a 0.150 M solution? (Assume that the volumes are additive.)
> Suppose 325 mL of 0.150 M NaOH is needed for your experiment. How would you prepare this if all that is available is a 1.01 M NaOH solution?
> How would you prepare 275 mL of 0.350 M NaCl solution using an available 2.00 M solution?
> For convenience, one form of sodium hydroxide that is sold commercially is the saturated solution. This solution is 19.4 M, which is approximately 50% by mass sodium hydroxide. What volume of this solution would be needed to prepare 3.50 L of 3.00 M NaOH
> Many laboratories keep bottles of 3.0 M solutions of the common acids on hand. Given the following molarities of the concentrated acids, determine how many milliliters of each concentrated acid would be required to prepare 225 mL of a 3.0 M solution of t
> A bottle of acid solution is labeled “3 M HNO3.” What are the substances that are actually present in the solution? Are any HNO3 molecules present? Why or why not?
> What is meant by the ion-product constant for water, Kw? What does this constant signify? Write an equation for the chemical reaction from which the constant is derived.
> When 1 mole of gaseous hydrogen chloride is dissolved in enough water to make 1 L of solution, approximately how many HCl molecules remain in the solution? Explain.
> When the volume of a given solution is tripled (by adding water), the new concentration of solute is the original concentration.
> When a concentrated stock solution is diluted to prepare a less concentrated reagent, the number of is the same both before and after the dilution.
> What volume of a 0.300 M CaCl2 solution is needed to prepare 240. mL of a 0.100 M Cl- solution?
> An experiment calls for 125 mL of 0.105 M NaCl solution. What mass of NaCl is required? What mass of NaCl would be required for 1.00 L of the same solution?
> Calculate the hydrogen ion concentration, in moles per liter, for solutions with each of the following pH values. a. pH = 2.75 b. pH = 12.8 c. pH = 4.33 d. pH = 9.61
> Write the conjugate base for each of the following acids. a. HBrO b. HNO2 c. HSO3- d. CH3NH3+
> What mass of solute is present in 225 mL of 0.355 M KBr solution?
> What mass of NaOH pellets is required to prepare 3.5 L of 0.50 M NaOH solution?
> Calculate the pOH value corresponding to each of the pH values listed, and tell whether each solution is acidic or basic. a. pH = 10.75 b. pH = 3.66 c. pH = 1.98 d. pH = 12.47
> Calculate the pH corresponding to each of the pOH values listed, and indicate whether each solution is acidic, basic, or neutral. a. pOH = 4.32 b. pOH = 8.90 c. pOH = 1.81 d. pOH = 13.1
> Write the conjugate base for each of the following acids: a. H2S b. HS2 c. NH3 d. H2SO3
> Write the conjugate acid for each of the following bases. a. ClO- b. Cl- c. ClO3- d. ClO4-
> Standard silver nitrate solutions are used in the analysis of samples containing chloride ion. How many grams of silver nitrate are needed to prepare 250. mL of a 0.100 M AgNO3 solution?
> If 42.5 g of NaOH is dissolved in water and diluted to a final volume of 225 mL, calculate the molarity of the solution.
> An alcoholic iodine solution (“tincture” of iodine) is prepared by dissolving 5.15 g of iodine crystals in enough alcohol to make a volume of 225 mL. Calculate the molarity of iodine in the solution.
> Standard solutions of calcium ion used to test for water hardness are prepared by dissolving pure calcium carbonate, CaCO3, in dilute hydrochloric acid. A 1.745-g sample of CaCO3 is placed in a 250.0-mL volumetric flask and dissolved in HCl. Then the sol
> How many grams of formaldehyde are in 113.1 mL of a 3.0 M aqueous solution of formaldehyde? The formula for formaldehyde is HCHO.
> A laboratory assistant needs to prepare 225 mL of 0.150 M CaCl2 solution. How many grams of calcium chloride will she need?
> For each pair of concentrations, tell which represents the more basic solution. a. [H+] = 2.02 * 10-7 M or [OH-] = 5.05 * 10-5 M b. [H+] = 1.79 * 10-5 M or [OH-] = 4.21 * 10-6 M c. [H+] = 1.25 * 10-12 M or [OH-] = 6.51 * 10-3 M
> Sulfuric acid has a great affinity for water, and for this reason, the most concentrated form of sulfuric acid available is actually a 98.3% solution. The density of concentrated sulfuric acid is 1.84 g/mL. What mass of sulfuric acid is present in 1.00 L
> For each pair of concentrations, tell which represents the more acidic solution. a. [H+] = 1.2 * 10-3 M or [H+] = 4.5 * 10-4 M b. [H+] = 2.6 * 10-6 M or [H+] = 4.3 * 10-8 M c. [H+] = 0.000010 M or [H+] = 0.0000010 M
> For each of the following solutions, the number of moles of solute is given, followed by the total volume of the solution prepared. Calculate the molarity of each solution. a. 0.754 mol KNO3; 225 mL b. 0.0105 mol CaCl2; 10.2 mL c. 3.15 mol NaCl; 5.00
> For each of the following solutions, the number of moles of solute is given, followed by the total volume of the solution prepared. Calculate the molarity of each solution. a. 0.521 mol NaCl; 125 mL b. 0.521 mol NaCl; 250. mL c. 0.521 mol NaCl; 500. m
> To prepare 500. mL of 1.02 M sugar solution, which of the following would you need? a. 500. mL of water and 1.02 mole of sugar b. 1.02 mole of sugar and enough water to make the total volume 500. mL c. 500. g of water and 1.02 mole of sugar d. 0.51 m
> Write the conjugate acid for each of the following bases: a. PO43- b. IO3- c. NO3- d. NH2-
> A solution labeled “0.25 M AlCl3” would contain mole(s) of Al3+ and mole(s) of Cl- in each liter of the solution.
> A solution you used in last week’s lab experiment was labeled “3 M HCl.” Describe in words the composition of this solution.
> A solvent sold for use in the laboratory contains 0.95% of a stabilizing agent that prevents the solvent from reacting with the air. What mass of the stabilizing agent is present in 1.00 kg of the solvent?
> The “Chemistry in Focus” segment Plants Fight Back discusses how tobacco plants under attack by disease produce salicylic acid. Examine the structure of salicylic acid and predict whether it behaves as a monoprotic or a diprotic acid.
> What mass of each solute is present in 285 g of a solution that contains 5.00% by mass NaCl and 7.50% by mass Na2CO3?
> Hydrogen peroxide solutions sold in drugstores as an antiseptic typically contain 3.0% of the active ingredient, H2O2. Hydrogen peroxide decomposes into water and oxygen gas when applied to a wound according to the balanced chemical equation 2H2O2(aq)
> How many grams of KBr are contained in 125 g of a 6.25% (by mass) KBr solution?
> A solution is to be prepared that will be 4.50% by mass calcium chloride. To prepare 175 g of the solution, what mass of calcium chloride will be needed?
> If 67.1 g of CaCl2 is added to 275 g of water, calculate the mass percent of CaCl2 in the solution.
> Write the formula for the hydronium ion. Write an equation for the formation of the hydronium ion when an acid is dissolved in water.
> Consider the iron alloy described in Question 19. Suppose it is desired to prepare 1.00 kg of this alloy. What mass of each component would be necessary? From 19: A sample of an iron alloy contains 92.1 g Fe, 2.59 g C, and 1.59 g Cr. Calculate the perce
> A sample of an iron alloy contains 92.1 g Fe, 2.59 g C, and 1.59 g Cr. Calculate the percent by mass of each component present in the alloy sample.
> In each of the following chemical equations, identify the conjugate acid–base pairs. a. NH3(aq) + H2O(l) ⇌ NH4+(aq) + OH-(aq) b. PO43-(aq) + H2O(l) ⇌ HPO42-(aq) + OH-(aq) c. C2H3O2-(aq) + H2O(l) ⇌ HC2H3O2(aq) + OH-(aq)
> Calculate the mass, in grams, of solute present in each of the following solutions. a. 375 g of 1.51% ammonium chloride solution b. 125 g of 2.91% sodium chloride solution c. 1.31 kg of 4.92% potassium nitrate solution d. 478 mg of 12.5% ammonium nit
> A solution that is 9% by mass glucose contains 9 g of glucose in every g of solution.
> How do we define the mass percent composition of a solution? Give an example of a solution, and explain the relative amounts of solute and solvent present in the solution in terms of the mass percent composition.
> Which of the following acids have relatively strong conjugate bases? a. HCN b. H2S c. HBrO4 d. HNO3
> The label “concentrated H2SO4” on a bottle means that there is a relatively amount of H2SO4 present in the solution.
> A solution is a homogeneous mixture and, unlike a compound, has composition.
> If additional solute is added to a(n) solution, it will dissolve.
> What does it mean to say that a solution is saturated with a solute?
> Which of the following do not represent a conjugate acid–base pair? For those pairs that are not conjugate acid–base pairs, write the correct conjugate acid–base pair for each species in the pair. a. H2SO4, SO42- b. H2PO4-, HPO42- c. HClO4, Cl- d. NH
> Which of the following do not represent a conjugate acid–base pair? For those pairs that are not conjugate acid–base pairs, write the correct conjugate acid–base pair for each species in the pair. a. HI, I- b. HClO, HClO c. H3PO4, PO43- d. H2CO3, CO3
> In a solution, the substance present in the largest amount is called the , whereas the other substances present are called the .
> Suppose you dissolved a teaspoon of sugar in a glass of water. Which substance is the solvent? Which substance is the solute?
> Gaseous phosphorus pentachloride decomposes according to the reaction PCl5(g) ⇌ PCl3(g) + Cl2(g) The equilibrium system was analyzed at a particular temperature, and the concentrations of the substances present were determined to be [PCl5] = 1.1 * 10-2
> For the reaction N2(g) + 3Cl2(g) ⇌ 2NCl3(g) an analysis of an equilibrium mixture at a particular temperature is performed. It is found that [NCl3] = 1.9 * 10-1 M, [N2] * 1.4 * 10-3 M, and [Cl2] = 4.3 * 10-4 M. Calculate K for the reaction.
> True or false? The position of a heterogeneous equilibrium does not depend on the amounts of pure solid or pure liquid reactants or products present because the concentrations of pure solids and liquids cannot change.
> Write the equilibrium expression for each of the following reactions. a. 2O3( g) ⇌ 3O2( g) b. CH4( g) + 2O2( g) ⇌ CO2( g) + 2H2O( g) c. C2H4( g) + Cl2( g) ⇌ C2H4Cl2( g)
> Write the equilibrium expression for each of the following reactions. a. H2( g) + Br2( g) ⇌ 2HBr( g) b. 2H2( g) + S2( g) ⇌ 2H2S( g) c. H2( g) + C2N2( g) ⇌ 2HCN( g)
> How does an increase in temperature result in an increase in the number of successful collisions between reactant molecules? What does an increase in temperature mean on a molecular basis?
> How does the collision model account for the fact that a reaction proceeds faster when the concentrations of the reactants are increased?
> When writing a chemical equation for a reaction that comes to equilibrium, how do we indicate symbolically that the reaction is reversible?
> For the reaction CaCO3(s) ⇌ CaO(s) + CO2(g) the equilibrium constant K has the form K = [CO2]. Using a handbook to find density information about CaCO3(s) and CaO(s), show that the concentrations of the two solids (the number of moles contained in 1 L o
> Many sugars undergo a process called mutarotation, in which the sugar molecules interconvert between two isomeric forms, finally reaching an equilibrium between them. This is true for the simple sugar glucose, C6H12O6, which exists in solution in isomeri