Solving Equilibrium Concentrations ( Case 1)

1. Solving Equilibrium Concentrations (Case 1) SCH4U0

2. Solving Equilibrium Concentrations • To determine the equilibrium concentrations of a system, given the starting conditions, we need a few tools • The K value • The reaction quotient and the equilibrium law • An ICE chart • Algebra techniques • Every equilibrium problem can be approached the same way • Regardless of the what the system is (dissolving, chemical reaction, acid/base, etc…) • You might need to use different tools to solve along the way though

3. Sample Problem • To illustrate the approach we will take, lets look at a sample situation • If we place 4.00 mol of bromine and iodine gases in a 2.00 L container at 150ºC, what will the equilibrium concentrations of each compound be? • Since we know K, will we now need; • Q, to determine which concentrations change, and how • An ICE chart

4. Sample Problem • If we place 4.00 mol of bromine and iodine gases in a 2.00 L container at 150ºC, what will the equilibrium concentrations of each compound be? Q < K, reaction shifts right

5. Sample Problem • From our ICE chart we have expressions for each of the equilibrium concentrations. • These can be subbed into the equilibrium law, since all of the concentrations in that equation are at equilibrium • This is one equation with one variable (since we know K) • Thus we can solve it using algebra • We need to choose the appropriate mathematical tools to use

6. Flow Chart • Choosing the appropriate mathematical tools depends on the type of equation you now have • We will analyze three different cases, and what tools are useful for solving them

7. Sample Problem – Case 1 • Our problem is a case 1; • We can simplify the equation using a square root

8. Sample Problem – Case 1 • Now we have two solutions, both of which initially seem ok • But one of them does not make physical sense with our situation • To see this lets look back at our equilibrium concentrations from the ICE chart • x cannot be larger than 2.00, or else we will have less than 0 moles of bromine and iodine, which is not physically possible extraneous

9. Practice • If 6.00 mol (each) of and , and 2.00 mol of are placed in a 2.00 L container at SATP, what will the equilibrium concentration of hydrogen fluoride be? Q < K, shifts right

10. Practice

11. Practice – Case 1

12. Practice – Case 1 • Now we have two solutions, both of which initially seem ok • But one of them does not make physical sense with our situation • To see this lets look back at our equilibrium concentrations from the ICE chart • x cannot be larger than 3.00, or else we will have less than 0 moles of fluorine and hydrogen, which is not physically possible extraneous