Chemistry Ch18&19 Exam

Le Châtelier's principle states that if a stress, such as a change in temperature, pressure, or concentration, is applied to a system at equilibrium, the system will shift in a way that counteracts the stress and restores equilibrium. In other words, if a stress is applied to a system, the system will adjust itself to relieve the stress and maintain equilibrium. This principle is widely used to predict and explain the behavior of chemical reactions and equilibria.

The solubility product constant is the correct answer because it specifically refers to the equilibrium constant for the dissolving of a sparingly soluble ionic compound in water. This constant represents the equilibrium between the dissolved ions and the undissolved solid, and is used to calculate the solubility of the compound. The solubility product constant is a characteristic property of the compound and is independent of the amount of solid present.

The common ion effect is the phenomenon where the solubility of a substance is decreased when a common ion is added to the solution. This occurs because the presence of the common ion reduces the concentration of the dissolved substance, shifting the equilibrium towards the solid form. As a result, the solubility of the substance is lowered.

The law of chemical equilibrium states that at a given temperature, a chemical system may reach a state in which a particular ratio of reactant and product concentrations has a constant value. This means that the forward and reverse reactions are occurring at equal rates, resulting in a dynamic equilibrium where the concentrations of reactants and products remain constant over time. The equilibrium constant is a numerical value that represents the ratio of product concentrations to reactant concentrations at equilibrium, and it is determined by the stoichiometry of the balanced equation for the reaction.

A reversible reaction is a reaction that can occur in both the forward and the reverse directions. This means that the reactants can form products, but the products can also react to form the original reactants. The equilibrium constant is a measure of the extent to which a reversible reaction proceeds in the forward or reverse direction. Therefore, the answer "reversible reaction" is the correct choice as it best describes a reaction that can occur in both directions.

Buffers are solutions that are able to resist changes in pH when small amounts of acid or base are added to them. They contain a weak acid and its conjugate base, or a weak base and its conjugate acid. When an acid is added to a buffer solution, the weak base in the buffer reacts with the acid to form its conjugate acid, preventing a significant change in pH. Similarly, when a base is added, the weak acid in the buffer reacts with the base to form its conjugate base, again preventing a significant change in pH. Therefore, buffers do indeed resist changes in pH, making the statement true.

A neutral solution contains an equal number of hydroxide ions and hydrogen ions, resulting in a balanced pH level of 7. Therefore, the statement that a neutral solution contains more hydroxide ions than hydrogen ions is false.

A buffer system should contain equal amounts of acid and base, or slightly more base than acid, in order to effectively resist changes in pH. Having considerably more acid than base would result in an unbalanced buffer system, making it less effective in maintaining a stable pH. Therefore, the given statement is false.

The statement is true because different buffer systems are effective at different pH levels. Buffer systems are solutions that resist changes in pH when small amounts of acid or base are added. Each buffer system has a specific range of pH where it is most effective. Therefore, it is important to choose a buffer system that can maintain the desired pH level.

A buffer solution is designed to resist changes in pH when small amounts of acid or base are added. However, if large amounts of acid or base are added to a buffer solution, it will not be able to effectively resist the change in pH and the pH of the solution will be significantly altered. Therefore, the statement that a buffer solution changes pH only a small amount even if large amounts of acid or base are added is incorrect.

A buffer solution is a solution that resists changes in pH when small amounts of acid or base are added to it. It consists of a weak acid and its conjugate base, or a weak base and its conjugate acid. In the given example, acetic acid is a weak acid and sodium acetate is its conjugate base. When combined, they create a buffer solution that can maintain a relatively constant pH when small amounts of acid or base are added. Therefore, the statement is true.

A buffer is a solution that resists changes in pH when small amounts of acid or base are added to it. It consists of a weak acid and its conjugate base. The weak acid can donate hydrogen ions to neutralize any added base, while the conjugate base can accept hydrogen ions to neutralize any added acid. This allows the buffer to maintain a relatively constant pH. Therefore, the statement that a buffer can be a mixture of a weak acid and its conjugate base is true.

The conductivity of a solution is directly related to the concentration of ions present in the solution. In this case, when the electrodes are placed in acid A and the bulb glows dimly, it indicates that acid A has a lower concentration of ions and therefore lower conductivity. On the other hand, when the electrodes are placed in acid B and the bulb glows more brightly, it suggests that acid B has a higher concentration of ions and therefore higher conductivity. This implies that acid B is stronger than acid A in terms of ion concentration and conductivity.

The pH of a solution is a measure of its acidity or alkalinity. It is determined by the concentration of H+ ions in the solution. The pH scale ranges from 0 to 14, with values below 7 indicating acidity, values above 7 indicating alkalinity, and a pH of 7 indicating neutrality. In this case, the H+ ion concentration is given as 1.00 x 10^-5 M. To find the pH, we take the negative logarithm (base 10) of the H+ ion concentration. In this case, the pH is equal to -log(1.00 x 10^-5) = 5.00. Therefore, the correct answer is 5.00.

The pOH of a solution is calculated by taking the negative logarithm of the hydroxide ion concentration. In this case, the pOH is 4.50. To find the hydrogen ion concentration (H+), we can use the relationship between pOH and pH. pH + pOH = 14. Therefore, the pH of the solution is 9.50 (14 - 4.50). The hydrogen ion concentration can be calculated by taking the antilogarithm (inverse logarithm) of the pH. So, 10^-9.50 = 3.16 x 10^-10 M.

The H+ concentration of an aqueous solution can be calculated using the ion product constant for water, KW. KW is equal to the concentration of H+ multiplied by the concentration of OH-. In this case, the concentration of OH- is given as 1 x 10-5 M. Since KW is known to be 1 x 10-14, we can rearrange the equation to solve for the concentration of H+. By dividing KW by the concentration of OH-, we find that the H+ concentration is 1 x 10-9 M.

Compounds formed from active metals and hydroxide ions are strong bases because active metals have a strong tendency to donate electrons and hydroxide ions (OH-) are strong bases themselves. When active metals react with water, they form metal hydroxides which dissociate completely in water, releasing hydroxide ions. These hydroxide ions then react with water molecules, increasing the concentration of hydroxide ions in the solution. This high concentration of hydroxide ions makes the solution highly alkaline and therefore a strong base.

A weak acid is a substance that only partially dissociates in water, meaning it forms a mixture of molecules and ions. This is in contrast to a strong acid, which completely dissociates into ions. Therefore, the correct answer is that a weak acid produces a mixture of molecules and ions.

Sulfuric acid is a strong acid, which means it completely ionizes in water to produce a high concentration of hydrogen ions (H+). The conjugate base of sulfuric acid is the sulfate ion (SO4^2-). Since sulfuric acid is a strong acid, it donates its proton (H+) very easily, resulting in a weak conjugate base. Therefore, the correct answer is that the conjugate base of sulfuric acid is weak.

An acid is a substance that contains more hydrogen ions (H+) than hydroxide ions (OH-). This is because acids donate H+ ions when dissolved in water. Therefore, the given statement "Contains more hydrogen ions than hydroxide ions" accurately describes an acid.

The given answer, "acid," is correct because acids react with certain metals to produce hydrogen gas. This reaction is known as metal-acid reaction. Acids have a pH less than 7 and can donate protons (H+) in a chemical reaction. When an acid reacts with a metal, it displaces hydrogen from the acid, leading to the formation of metal salts and hydrogen gas. Therefore, the statement "Reacts with certain metals" is characteristic of acids.

The taste of sourness is commonly associated with acidic substances. Acids are known to have a sour taste, while bases usually have a bitter taste. Therefore, the correct answer is "acid" as it explains the sour taste mentioned in the question.

A base is a substance that tastes bitter. Bitter taste is a characteristic property of bases. Acids, on the other hand, typically taste sour. Since the given substance tastes bitter, it can be concluded that it is a base.

The equivalence point of a titration refers to the point at which the stoichiometric quantities of the reactants have been completely reacted. At this point, the moles of the acid and base are in the exact ratio required by the balanced chemical equation. It is indicated by a sudden change in the pH of the solution being titrated. This is different from the end point, which is the point at which the indicator changes color, and the acid-base indicator, which is a substance that changes color depending on the pH of the solution.

The end point in a titration is the point at which an indicator changes color. This indicates that the reaction between the acid and base is complete and that the solution has reached the desired pH. The end point is used to determine the equivalence point, which is the point at which the acid and base have reacted in stoichiometric proportions. The end point is an important indicator of when to stop the titration and calculate the concentration of the unknown solution.

A standard solution is a solution of known concentration that is used to determine the concentration of another substance through a process called titration. In titration, the standard solution is slowly added to the solution of unknown concentration until a chemical reaction between the two is complete. The point at which the reaction is complete is called the equivalence point. The standard solution is used to determine the concentration of the unknown solution by measuring the volume of standard solution needed to reach the equivalence point.

Titration is a method used to determine the concentration of a solution by adding a standardized solution (known as the titrant) to the solution of unknown concentration until a reaction between the two is complete. In this case, the neutralization reaction between an acid and a base is used to determine the concentration of the solution. The point at which the reaction is complete is called the equivalence point, which is often detected using an acid-base indicator. Titration allows for accurate and precise determination of the concentration of a solution by comparing it to a known standard solution.

The law of chemical equilibrium states that at a given pressure, a chemical system may reach a state in which a particular ratio of reactant to product concentrations has a constant value. This statement is true.

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If an equilibrium constant has a value less than one, it indicates that the concentration of products at equilibrium is lower than the concentration of reactants. This means that the reaction is more likely to favor the reactants and proceed in the reverse direction. Therefore, the statement "the reactants are favored at equilibrium" is true in this case.

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A heterogeneous equilibrium refers to a chemical reaction where the reactants and products are present in different states. This means that they can exist in different phases, such as solid, liquid, or gas. In contrast, a homogeneous equilibrium occurs when all the reactants and products are in the same state. Therefore, the statement that a heterogeneous equilibrium means that reactants and products are present in more than one state is true.

Based on the given information, the equilibrium constant for the reaction is 49.7. The equilibrium constant is defined as the ratio of the concentrations of products to the concentrations of reactants at equilibrium. Therefore, if the equilibrium constant is greater than 1, it indicates that the concentration of products is greater than the concentration of reactants at equilibrium. Since the given equilibrium constant is 49.7, it suggests that the concentration of products will be greater than the concentration of reactants at equilibrium. Therefore, the correct answer is False.

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The solubility product expression describes the equilibrium between a sparingly soluble ionic compound and its ions in solution. This expression is used to calculate the solubility of the compound and determine the concentration of its ions in the solution at equilibrium. It is based on the principle that the product of the ion concentrations raised to their respective stoichiometric coefficients is equal to a constant value at equilibrium. Therefore, the correct answer is "its ions in solution."

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A large value for Keq indicates that the products are favored in the reaction. Keq, or the equilibrium constant, is a measure of the ratio of product concentrations to reactant concentrations at equilibrium. A large value of Keq means that the equilibrium position is shifted towards the products, indicating that the products are favored over the reactants in the reaction.

The value of any equilibrium constant is correct only at a specific temperature because temperature affects the rate at which reactions occur and the balance between reactants and products. Changing the temperature alters the energy of the particles, which can either speed up or slow down the reaction. Therefore, the equilibrium constant, which represents the ratio of the concentrations of products and reactants at equilibrium, is only valid at a specific temperature.

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All of the choices can cause the solubility of a substance to decrease. A decrease in temperature generally reduces the kinetic energy of the particles, making them less likely to overcome the attractive forces and dissolve. A decrease in pressure can also decrease solubility by reducing the number of gas molecules available to dissolve in a liquid. The presence of a common ion can cause a decrease in solubility through the common ion effect, where the presence of an ion already in solution reduces the solubility of a compound containing the same ion. Therefore, all of these factors can contribute to a decrease in solubility.

The solubility product constant is a value that represents the equilibrium between a solute and its ions in a saturated solution. It is determined by multiplying the concentrations of the ions raised to their respective stoichiometric coefficients. The ion product, on the other hand, is calculated by multiplying the concentrations of the ions in any given solution. By comparing the ion product to the solubility product constant, it can be determined whether a substance will precipitate. If the ion product is greater than the solubility product constant, the solution is supersaturated and precipitation will occur. If the ion product is less than the solubility product constant, the solution is unsaturated and no precipitation will occur.

The solubility product of aluminum sulfate Al2(SO4)3 is given by the expression "chemical equilibrium constant, equal". This means that the solubility product is equal to the product of the concentrations of the ions raised to their stoichiometric coefficients in the balanced chemical equation. This expression represents the state of equilibrium between the dissolved ions and the solid compound, indicating that the compound is in a saturated solution and no further dissolution or precipitation will occur.

At equilibrium, the concentrations of reactants and products are constant, meaning they do not change over time. However, this does not imply that the amounts or concentrations of reactants and products are equal. The equilibrium constant, which is a ratio of the concentrations of products and reactants at equilibrium, determines the extent of the reaction and whether the reactants or products are present in higher concentrations. Therefore, the concentrations can be unequal at equilibrium depending on the specific reaction and its equilibrium constant.

Chemical equilibrium is a state in which the forward and reverse reactions of a chemical reaction occur at equal rates, resulting in a balance between the reactants and products. This means that the concentration of the reactants and products remains constant over time. In other words, the reaction is in a state of dynamic balance, where the rate of the forward reaction is equal to the rate of the reverse reaction. This state is often represented by the double arrow symbol (⇌) in chemical equations.

A reversible reaction is a reaction that can occur in both the forward and the reverse directions. In other words, the products of the reaction can react with each other to form the original reactants. This type of reaction reaches a state of chemical equilibrium, where the forward and reverse reactions are occurring at the same rate. The reaction can be reversed by changing the conditions, such as temperature or pressure. Therefore, "reversible reaction" is the correct answer for this question.

A heterogeneous equilibrium refers to an equilibrium reaction where the reactants and products are present in more than one physical state. This means that the substances involved in the reaction exist as a mixture of solids, liquids, and/or gases. In a heterogeneous equilibrium, the concentrations of the reactants and products may vary depending on the phase they are in. This is in contrast to a homogeneous equilibrium where all the reactants and products are in the same phase.

Barium sulfate is used when X rays are taken of the digestive system, based on the common ion effect. This effect occurs when the addition of a common ion, in this case, the sulfate ion, reduces the solubility of a slightly soluble compound, such as barium sulfate. By adding barium sulfate, which is not very soluble in water, to the digestive system, it helps to enhance the contrast in the X-ray images, allowing for better visualization of the digestive system.

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A common ion refers to an ion that is present in multiple ionic compounds in solution. When a common ion is added to a solution, it can decrease the solubility of a compound by shifting the equilibrium towards the formation of a precipitate. This is due to Le Châtelier's principle, which states that a system will adjust to counteract any changes imposed upon it. The presence of a common ion reduces the concentration of one of the ions involved in the equilibrium, causing the equilibrium to shift in the opposite direction to restore the balance.