Chemical Equilibrium

Transcription

1 RB # Row/Seat Chemical Equilibrium Name Date Per. For items 1-8, underline the term inside the parentheses that makes each statement true. 1. At equilibrium, the rate of the forward reaction is (equal to, greater than) the rate of the reverse reaction. 2. The equilibrium constant for a given reaction at a given temperature is the (product, quotient) of the specific rate constant for the forward reaction and the specific rate constant for the reverse reaction. 3. The exponents used in the expression for the equilibrium constant are the (subscripts, coefficients) of the reactants and products. 4. If a reaction tends to go toward completion, the rate of the forward reaction is (greater than, less than, equal to) the rate of the reverse reaction before equilibrium is reached. 5. If K eq = 1.2 x 10 5, the concentration of the reactants is (greater than, less than) the concentration of the products at equilibrium. 6. At temperature T 1, K eq for a certain reaction is At temperature T 2, K eq for the same reaction is 4.7. By changing the temperature from T 1 to T 2, the equilibrium will shift in favor of the (reactants, products). 7. If the reaction H 2(g) + Cl 2(g) 2HCI (g) + heat is at equilibrium, a, decrease in (volume, temperature) will produce a shift in equilibrium toward the right. 8. An increase in pressure on the system 2CO 2(g) 2CO (g) + 0 2(g) at equilibrium results in an equilibrium shift toward the (left, right). Answer or complete each of the following items. 9. What factors can affect the equilibrium of a reaction? 10. A reversible one-step reaction occurs between carbon monoxide gas, CO, and hydrogen gas, H 2, to produce methane gas, CH 4, and gaseous water. Using this information, fill in the diagram according to the following guidelines a. Within the ovals, write the balanced equation for the reaction. 5 b. Label forward and reverse reactions on the lines provided. (Write the words.) c. In the rectangles, write the words reactants or products, as appropriate, to represent both the forward and reverse reactions. reaction reaction Chemistry-2 Chemical Equilibrium Page 1

2 11. Write the expression for the equilibrium constant for the reaction in question In the reaction in question 10, if the volume of the reaction vessel and temperature are kept constant and the pressure on the system is increased, a. the concentrations of which substances would be affected? (reactants or products) b. in which direction will the equilibrium shift? c. which substance(s) will show an increase in concentration when equilibrium is reestablished? 13. Consider the equilibrium equation for the reaction: 4HCl (g) + 0 2(g) + heat 2C1 2(g) + 2H 2 0 (g) a. If the temperature is increased, the reaction will favor the formation of (reactants or products) b. Which reaction requires an input of energy? (forward or reverse) 14. The Haber process is used for the industrial production of ammonia. It involves the reaction: N 2(g) + 3H 2 2NH 3 + energy. a. why is NH 3 removed as it is formed? b. why is the use of a catalyst considered one of the optimum conditions for this process? c. what is the effect on the relative amounts of product and reactant if the catalyst is removed? 15. Given K eq = [NO] 4 [H 2 O] 6 [NH 3 ] 4 [O 2 ] 5 a. Write the chemical equation for the reversible reaction having the given K eq. b. At a certain temperature the concentrations of NO and NH 3 are equal, and the concentration of H 2 O and O 2 are 2.0 M and 3.0 M respectively. What is the value of K eq at this temperature? Chemistry-2 Chemical Equilibrium Page 2

3 Equilibrium Vocabulary chemical equilibrium ion product reversible reaction coefficient K eq saturated solution concentration K sp shift dissociation equation Le Châtelier s principle solubility product constant double arrow mass-action expression solubility product expression equilibrium constant precipitate stress Haber process rate A chemical change in which the reactants can be re-formed from the products is called a(n) (1). When forward and reverse reactions occur at the same (2), a state of (3) exists. A(n) (4) is used in an equation to symbolize this state. According to the law of chemical equilibrium, the, (5) symbolized by, (6) is numerically equal to the fraction formed by the (7) of the reactants and the products raised to a power equal to the (8) of each in the balanced equation. This fraction is called the. (9) When conditions such as temperature are changed, a chemical reaction is said to be placed under a(n). (10) Under such changing conditions, equilibrium can undergo a(n) (11) in the direction that tends to counteract the imposed changes. This generalization is known as, (12) which has been applied to the manufacture of ammonia by a method called the. (13) The concentration of an ionic solid in contact with a(n) (14) of that solid is a constant. This constant can be combined with the solution equilibrium constant to produce the, (15) whose symbol is. (16) Given a(n) (17) showing the formation of ions from a solid, we may write an expression, called a(n), (18) to show what concentrations of ions, raised to appropriate powers and divided, produce the constant. Such an expression is sometimes called a(n). (19) Chemistry-2 Chemical Equilibrium Page 3

4 Chemical Equilibrium For items 1-8, underline the term inside the parentheses that makes each statement true. 1. At equilibrium, the rate of the forward reaction is (equal to, greater than) the rate of the reverse reaction. 2. The equilibrium constant for a given reaction at a given temperature is the (product, quotient) of the specific rate constant for the forward reaction and the specific rate constant for the reverse reaction. 3. The exponents used in the expression for the equilibrium constant are the (subscripts, coefficients) of the reactants and products. 4. If a reaction tends to go toward completion, the rate of the forward reaction is (greater than, less than, equal to) the rate of the reverse reaction before equilibrium is reached. 5. If K eq = 1.2 x 10 5, the concentration of the reactants is (greater than, less than) the concentration of the products at equilibrium. 6. At temperature T 1, K eq for a certain reaction is At temperature T 2, K eq for the same reaction is 4.7. By changing the temperature from T 1 to T 2, the equilibrium will shift in favor of the (reactants, products). 7. If the reaction H 2(g) + Cl 2(g) 2HCI (g) + heat is at equilibrium, a, decrease in (volume, temperature) will produce a shift in equilibrium toward the right. 8. An increase in pressure on the system 2CO 2(g) 2CO (g) + 0 2(g) at equilibrium results in an equilibrium shift toward the (left, right). Answer or complete each of the following items. 9. What factors can affect the equilibrium of a reaction? temperature, pressure, concentration of reactants and/or products 10. A reversible one-step reaction occurs between carbon monoxide gas, CO, and hydrogen gas, H 2, to produce methane gas, CH 4, and gaseous water. Using this information, fill in the diagram according to the following guidelines a. Within the ovals, write the balanced equation for the reaction. 5 b. Label the forward and reverse reactions on the lines provided. forward reaction reactants CO (g) + 3H 2(g) products reverse reaction c. In the rectangles, write the words reactants or products, as appropriate, to represent both the forward and reverse reactions. 11. Write the expression for the equilibrium constant for the reaction in question 10. [CH 4 ] [H 2 O] K eq = [CO] [H 2 ] 3 products CH 4(g) + H 2 O (g) reactants Chemistry-2 Chemical Equilibrium Page 4

5 12. In the reaction in question 10, if the volume of the reaction vessel and temperature are kept constant and the pressure on the system is increased, a. the concentrations of which substances would be affected? all of them b. in which direction will the equilibrium shift? toward the right c. which substance(s) will show an increase in concentration when equilibrium is reestablished? CH 4 and H 2 O 13. Consider the equilibrium equation for the reaction: 4HCl (g) + 0 2(g) + heat 2C1 2(g) + 2H 2 0 (g) a. If the temperature is increased, the reaction will favor the formation of products (Cl 2, H 2 O) b. Which reaction requires an input of energy? the forward reaction 14. The Haber process is used for the industrial production of ammonia. It involves the reaction: N 2(g) + 3H 2 2NH 3 + energy. a. why is NH 3 removed as it is formed? the removal of products shifts equilibrium toward the formation of more product b. why is the use of a catalyst considered one of the optimum conditions for this process? it lowers the activation energy which speeds up the reaction. c. what is the effect on the relative amounts of product and reactant if the catalyst is removed? none 15. Given K eq = [NO] 4 [H 2 O] 6 [NH 3 ] 4 [O 2 ] 5 a. Write the chemical equation for the reversible reaction having the given K eq. 4 NH O 2 4 NO + 6 H 2 O b. At a certain temperature the concentrations of NO and NH 3 are equal, and the concentration of H 2 O and O 2 are 2.0 M and 3.0 M respectively. What is the value of K eq at this temperature? Since [NO] = [NH3], they cancel out and are not part of the equation. K eq = [H 2 O] 6 [O 2 ] 5 [2.O] 6 = = 64 = 0.26 [3.0] Chemistry-2 Chemical Equilibrium Page 5

6 Equilibrium Vocabulary chemical equilibrium ion product reversible reaction coefficient K eq saturated solution concentration K sp shift dissociation equation Le Châtelier s principle solubility product constant double arrow mass-action expression solubility product expression equilibrium constant precipitate stress Haber process rate A chemical change in which the reactants can be re-formed from the products is called a(n) (1). When forward and reverse reactions occur at the same (2), a state of (3) exists. A(n) (4) is used in an equation to symbolize this state. According to the law of chemical equilibrium, the, (5) symbolized by, (6) is numerically equal to the fraction formed by the (7) of the reactants and the products raised to a power equal to the (8) of each in the balanced equation. This fraction is called the. (9) When conditions such as temperature are changed, a chemical reaction is said to be placed under a(n). (10) Under such changing conditions, equilibrium can undergo a(n) (11) in the direction that tends to counteract the imposed changes. This generalization is known as, (12) which has been applied to the manufacture of ammonia by a method called the. (13) The concentration of an ionic solid in contact with a(n) (14) of that solid is a constant. This constant can be combined with the solution equilibrium constant to produce the, (15) whose symbol is. (16) Given a(n) (17) showing the formation of ions from a solid, we may write an expression, called a(n), (18) to show what concentrations of ions, raised to appropriate powers and divided, produce the constant. Such an expression is sometimes called a(n). (19) reversible reaction 1. rate 2. chemical equilibrium 3. double arrow 4. equilibrium constant K eq concentration 7. coefficient 8. mass-action expression 9. stress 10. shift 11. Le Châtelier s principle Haber process precipitate 14. solubility product constant K sp dissociation equation 17. solubility product expression ion product Chemistry-2 Chemical Equilibrium Page 6

7 Chemistry-2 Chemical Equilibrium Page 7