2 H_2 O_2 (aq) rightarrow 2 H_2 O (l) + O_2 (g) delta H degree = - 196 kJ/mol_rx

Question

2 H_2 O_2 (aq) rightarrow 2 H_2 O (l) + O_2 (g) delta H degree = - 196 kJ/mol_rxn The decomposition of H_2 O_2 (aq) is represented by the equation above. A student monitored the decomposition of a 1.0 L sample of H_2 O_2 (aq) at a constant temperature of 300. K and recorded the concentration of H_2 O_2 as a function of time. The results are given in the table below. Which of the following identifies the element(s) being oxidized and reduced in the reaction? (A) Hydrogen is oxidized and oxygen is reduced. (B) Oxygen is oxidized and hydrogen is reduced. (C) Oxygen is both oxidized and reduced. (D) No elements arc oxidized or reduced: the reaction is not a redox reaction. The O_2 (g) produced from the decomposition of the 1.0 L sample of H_2 O_2 (aq) is collected in a previously evacuated 10.0 L flask at 300. K. What is the approximate pressure in the flask after 400. s? (For estimation purposes, assume that 1.0 mole of gas in 1.0 L exerts a pressure of 24 atm at 300 K.) (A) 1.2 atm (B) 2.4 atm (C) 12 atm (D) 24 atm Which of the following statements is a correct interpretation of the data regarding how the order of the reaction can be determined? (A) The reaction must be first order because there is only one reactant species. (B) The reaction is first order if the plot of In [H_2 O_2] versus time is a straight line. (C) The reaction is first order if the plot of 1/[H_2 O_2] versus time is a straight line. (D) The reaction is second order because 2 is the coefficient of H_2 O_2 in the chemical equation. The reaction is thermodynamically favorable. The signs of delta G degree and delta S degree for the reaction arc which of the following?

Explanation / Answer

Initial [H2O2] = 2.7 M

After 400.s [H2O2] = 1.7 M

SO, moles of H2O2 consumed during this time = 2.7 - 1.7 = 1.0 mol

Accroding to balanced equation,

2.0 mol of H2O2 on decompostion forms 1.0 mol of O2

Then, 1.0 mol of H2O2 on decomposition forms 1/2 mol of O2

It is given that,

1.0 mol of O2 gas in 1.0 L exerts a pressure of 24 atm

Then, 1/2 mol of O2 gas in 1.0 L exerts a pressure 12 atm

Now, 1/2 mol of O2 gas in 10.0 L exerts a pressure of 1.2 atm

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