Consider the following problem:
Target: 2NOCl(g) ? N2(g)+ O2(g)+Cl2 (g) ?Hrxn= ?
Steps:
1. 1/2 N2(g) + 1/2 O2(g)? NO(g) ?H= 90.3 kJ
2. NO(g) + 1/2 Cl2(g) ? NOCl(g) ?H= -38.6 kJ
As you determine the ¥ÄHrxn value for the target equation above, what must be done to step 2?
Question options:
a. Step 2 requires no change
b. Step 2 should be only multiplied by 2
c. Step 2 should be reversed and multiplied by 1/2.
d. Step 2 should be reversed and multiplied by 2.
e. Step 2 should be only reversed
To determine the ΔHrxn value for the target equation, you need to consider the coefficients and the direction of the reactions in the given steps.
In step 2: NO(g) + 1/2 Cl2(g) → NOCl(g) ΔH = -38.6 kJ
The target equation involves the reverse reaction of step 2: NOCl(g) → NO(g) + 1/2 Cl2(g)
To reverse the reaction, you need to flip the equation and change the sign of ΔH: NO(g) + 1/2 Cl2(g) ← NOCl(g) ΔH = +38.6 kJ
Now, to determine the ΔH for the target equation, you need to add the ΔH values of step 1 and the reversed step 2. Since step 2 has been reversed, you should multiply it by a factor that preserves the stoichiometric ratio.
Therefore, the correct answer is:
c. Step 2 should be reversed and multiplied by 1/2.
To determine the ΔHrxn value for the target equation, the steps must be modified as required.
In step 2, the reaction should be reversed and multiplied by 2.
Therefore the correct answer is option d. Step 2 should be reversed and multiplied by 2.