Predicting relative forward and reverse rates of reaction. Ammonia and oxygen re
ID: 707214 • Letter: P
Question
Predicting relative forward and reverse rates of reaction. Ammonia and oxygen react to form nitrogen and water, like this: 4 NH3(9)+30) 2N2()6H20() Imagine 127. mmol of N2 and 381. mmol of H20 are added to an empty flask, and then answer the following questions. What is the rate of the reverse reaction before any N2 or H20 has been added to the flask? zero. Greater than zero, but less than the rate of the forward reaction. Greater than zero, and equal to the rate of the forward reaction. Greater than zero, and greater than the rate of the forward reaction. O Zero. What is the rate of the reverse reaction just after the N2 or H20 has been added to the flask? Greater than zero, but less than the rate of the forward reaction. Greater than zero, and equal to the rate of the forward reaction. Greater than zero, and greater than the rate of the forward reaction. O Zero. Greater than zero, but less than the rate of the forward reaction. Greater than zero, and equal to the rate of the forward reaction. Greater than zero, and greater than the rate of the forward reaction. None. Some, but less than 127, mmol. 127. mmol. More than 127. mmol. What is the rate of the reverse reaction at equilibrium? How much N2 is in the flask at equilibrium? Explanation Check O 2018 McGraw-HExplanation / Answer
Initially when there is nothing in the flask that is when the flask is empty there will not any reagents between which a reaction could occur. So initially when the flask is empty (before addition of N2 and H2O), the rate of both forward as well as reverse reaction is zero. Thus answer of first question is zero.
When N2 and H2O are added to the flask only the product side (right side of equation) reagents are present. Equilibrium will occur only when atleast some reactant side that is NH3 and O2 are also present. This will happen when reverse reaction rate is greater than zero. Also forward reaction rate will increase only when some NH3 and O2 are produced, so initially forward reaction rate will be less than reverse reaction rate.Thus answer of second question is greater than zero and greater than the rate of reverse reaction.
Always remember that at an equilibrium stage for any reaction, the rate of both forward as well as reverse reactions is greater than zero and also forward reaction rate will be equal to that of reverse reaction rate.Same will be in the present case.So answer is third option from top that is the rate of reverse reaction is greater than zero and also equal to that of forward reaction rate.
Since some N2 has been consumed to produce reactant side NH3 and O2 for achieving equilibrium state, so some amount of N2 will be left and it will be less than 127 mmol.