CHEM 121 Lecture Notes - Lecture 8: Ionic Compound, Strong Electrolyte, Sodium Chloride

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15 Nov 2016

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Nacl (s) --> na+ (aq) + cl- (aq) Ionic compounds behave as strong electrolytes; dissolve to give solution of. Most molecular compounds behave as nonelectrolytes; dissolve to give. Acids are one exception!: when acids dissolve into water, they want to carry h+ ions, weak electrolytes; dissolve to give some hydrated ions. The double-arrow in an equation (the yield line) is only double if there is an incomplete reaction. Any ionic compound if it dissolves at all, will be a strong electrolyte. An electrolyte dissolves in water giving a solution that can conduct electricity. A nonelectrolyte also dissolves in water, but gives a solution that does not conduct electricity. A precipitate is an insoluble solid that separates from solution. The net ionic equations tells the very concise story of what happens. Precipitate will always be between the cation on the rst compound and the anion of the second. Monoprotic acids have one hydrogen ion in the compound.

Related Questions

The Behavior of Substances in Water

Part 1:

Ammonia, NH₃, is a weak electrolyte. It forms ions in solution by reacting with water molecules to form the ammonium ion and hydroxide ion. Write the balanced chemical reaction for this process, including state symbols.
From everyday experience, you are probably aware that table sugar (sucrose), C₁₂H₂₂O₁₁, is soluble in water. When sucrose dissolves in water, it doesn’t form ions through any reaction with water. It just dissolves without forming ions, so it is a nonelectrolyte. Write the chemical equation for the dissolving of sucrose in water.
Both NH₃ and C₁₂H₂₂O₁₁ are soluble molecular compounds, yet they behave differently in an aqueous solution. Briefly explain why one is a weak electrolyte and the other is a nonelectrolyte.
Hydrochloric acid, HCl, is a molecular compound that is a strong electrolyte. Write the chemical reaction of HCl with water.
Compare the ammonia reaction with that of hydrochloric acid. Why are both of these substances considered electrolytes?
Explain why HCl is a strong electrolyte and ammonia is a weak electrolyte.
Classify each of the following substances as either ionic or molecular:

KCl
NH₃
CO₂
MgBr₂
HCl
Ca(OH)₂
PbS
HC₂H₃O₂

For those compounds above that, you classified as ionic, use the solubility rules to determine which are soluble.
The majority of ionic substances are solids at room temperature. Describe what you would observe if you placed a soluble ionic compound and an insoluble ionic compound in separate beakers of water.
Write the chemical equation(s), including state symbols, for what happens when each soluble ionic compound that you identified above is placed in water. Are these substances reacting with water when they are added to water?
How would you classify the soluble ionic compounds: strong electrolyte, weak electrolyte, or nonelectrolyte? Explain your answer.
Sodium chloride, NaCl, is a strong electrolyte, as is hydroiodic acid, HI. Write the chemical equations for what happens when these substances are added to water. m
Are NaCl and HI strong electrolytes because they have similar behavior in an aqueous solution? If not, describe, using words and equations, the different chemical process that takes place in each case.

Part 2:

You have two hypothetical molecular compounds, AX and AY. AX is a strong electrolyte and AY is a weak electrolyte. The compounds undergo the following chemical reactions when added to water.

AX (aq) + H₂O (l) → AH₂O⁺ (aq) + X⁻ (aq)

AY (aq) + H₂O (l) → AH₂O⁺ (aq) + Y⁻ (aq)

Explain how the relative amounts of AX ( aq ) and AY ( aq ) would compare if you had a beaker of water with AX and a beaker of water with AY.
How would the relative amounts of X⁻ ( aq) and Y⁻ ( aq) in the two beakers compare? Be sure to explain your answer.

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When equal molar amounts of these sets of compounds are mixed in aqueous solution, which will form a buffer solution? (A) HCl with NaCl (B) HCl with NaOH (C) NaOH with Na_2 CO_3 (D) NH_3 with NH_4 Cl The pH of a 0.0100 M solution of a weak acid, HA, is 3.76. What is the percent ionization of HA for this solution? (A) 0.017% (B) 0.58% (C) 1.7% (D) 5.8% Which is the most prevalent species in a 0.25 M aqueous solution of phosphoric acid, H_3 PO_4? (A) H_3 PO_4 (B) H_2 PO_4^- (C) HPO_4^2- (D) H_3 O^+ Which titration has an equivalence point with a basic pH? (A) titrating NH_3(aq) with HCl(aq) (B) titrating HNO_3(aq) with KOH(aq) (C) titrating HNO_2(aq) with KOH(aq) (D) titrating HClO_4 (aq) with Ca(OH)_2 (aq) Which figure best represents a concentrated aqueous solution of HI? (Water molecules are not shown.) A current of 0.150 A is passed through an aqueous CuSO_4 solution for 10.0 minutes. What mass of Cu is plated out? (Assume 100% yield.) (A) 0.000494 g (B) 0.0592 g (C) 0.0296 g (D) 0.0148 g The oxidation number of carbon changes from _____ in this redox reaction: 2NnO_4^- (aq) + 3C_2 O_4^2- (aq) + 4OH^- (aq) 2MNO_2 (s) + 6CO_3^2 (aq) + 2H O(I) (A) +6 to +4 (B) +4 and +3 (C) +3 to +4 (D) +3 to +6 Which species is the most powerful reducing agent at standard conditions? Na^+ (aq) + e^- rightarrow Na(s) E degree = -2.71 V Fe^2+ (aq) + 2e^- rightarrow Fe(s) E degree = -0.45 V O_2 (g) + 2H_2 O(l) + 4e^- rightarrow 4OH^- (aq) E degree = 0.40 V I_2 (s) + 2e^- rightarrow 2I^- (aq) E degree = 0.54 V (A) Na(s) (B) Fe^2+ (aq) (C) OH^- (aq) (D) I_2 (s) For this galvanic cell reaction 3HNO_2 (aq) + BrO_3^- (aq) rightarrow 3H^+(aq) + 3NO_3^- (aq) + Br^- (aq) the Nernst equation implies that the galvanic cell will have a more negative voltage if you: (A) increase the pH. (B) decrease the Br^- concentration (C) increase the BrO_3^-, concentration. (D) increase the NO_3^- concentration. The reaction Zn(s) + Ni^2+ (aq) rightarrow Zn^2 (aq) + Ni(s) occurs in the galvanic cell shown. Which statement is true? (A) Electrons flow to the Zn electrode. Na^+ ions flow toward the Ni electrode. (B) Electrons flow to the Zn electrode. Na^+ ions flow toward the Zn electrode. (C) Electrons flow to the Ni electrode. Na^+ ions flow toward the Ni electrode. (D) Electrons flow to the Ni electrode. Na^+ ions flow toward the Zn electrode.

Part A A fuel cell differs from a battery because the current is being generated from a reduction-oxidation (redox) reaction in which the reactant is consumed. A classic example of a fuel cell is the phosphoric acid fuel cell (PAFC), which have been used in stationary power generators, buses, and even submarines. Fuel cells require an electrolyte (similar to batteries) to carry electrically charged species between the electrodes, and a PAFC utilizes phosphoric acid (H3PO4) as its electrolyte. Phosphoric acid has three acidic protons that can dissociate in water, as highlighted in red here: H3PO4. However, it is considered a weak acid because some of the acid will remain in molecular form when dissolved in water. Write the complete ionic equation that depicts the dissociation of the first proton for the weak acid phosphoric acid (H3PO4). Make certain you include all charges for any ions produced. Express you answer as a chemical equation including phases. Titrations as analytical neutralization reactions Neutralization reactions can occur between any combination of weak/strong acids and bases. When we want to determine the concentration of a base in solution, we can apply the concept of neutralization by reacting the base with a known amount of an acid in the presence of an indicator (a compound that changes color depending on the pH). This method of determining the concentration of a base is called acid-base titration, and it can also be used to determine the concentration of an acid by titrating it with a known amount of base. A common acid to use for titrations is potassium hydrogen phthalate (written as KHP or KHPh; do not confuse the P for phosphorus). The reason KHP is common is because it is solid at room temperature, and we can accurately mass the amount that is added to solution. As a soluble salt, KHP completely dissociates to form a potassium ion (K+) and an acidic hydrogen phthalate ion (HPâ), which is a weak acid that has only one acidic hydrogen. This ionization is depicted below. KHP(s) â K+(aq)+HPâ(aq) Although ionization (the formation of ions) occurs as a result of acid dissociation for most weak acids, KHP ionizes before acid dissociation occurs. In other words, HPâ is a weak acid ion. Part C If you wanted to determine how much KOH (potassium hydroxide; a strong base) was dissolved in water, you could titrate it with a known amount of KHP (potassium hydrogen phthalate; a weak acid) until a color change indicates that the base is completely neutralized. The molecular equation below depicts this neutralization reaction. KHP(aq)+KOH(aq)âK2P(aq)+H2O(l) Write the net ionic equation that depicts the neutralization of the base by potassium hydrogen phthalate. Instead of using the entire chemical formula of phthalate, use HPâ to represent the acidic hydrogen phthalate ion and P2â to represent the phthalate ion. Express your answer as a net ionic equation including phases.

CHEM 121 Lecture Notes - Lecture 8: Ionic Compound, Strong Electrolyte, Sodium Chloride

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