A chemical reaction that is 1^st order in X is observed to have a rate of 2.2 ti

Question

A chemical reaction that is 1^st order in X is observed to have a rate of 2.2 times 10^-2 s^-1. If initial concentration of X is constant M 1.0 M, what is concentration of X after 205 s? a) 91 M b) 0.55 M c) 0.18 M d) 0.99 M e) 0.011 M A particular first-order reaction has a rate constant of 00109 hr^-1 What is the half-life for this reaction? a) 1.00 hr b) 63.8 hr c) 92.0 hr d) 0.0157 hr e) 0.0109 hr Consider the reaction: CaCl_2(s) + 2H_2O(l) CaCl_2 - 2H_2O(s) The equilibrium constant for the reaction as written is: a) K = [CaCl_2 middot 2H_2O]/[CaCl_2] [H_2O]^2 b) K = 1/[H_2O]^2 c) K = 1/2[H_2O] d) K = [H_2O]^2 e) K = [CaCl_2 middot 2H_2O]/[H_2O]^2 Consider the following reaction: CaCO_3(s) + 2HCl(aq) rightarrow CO_2(g) + CaCl_2(aq) + H_2O(l) + heat Which of the following is true? a) Increasing the temperature shifts the reaction towards products b) Adding helium to increase the pressure shifts the reaction towards reactants c) Adding more CaCO_3(s) shifts the reaction towards products reactants d) Moving the reaction to a smaller vessel shifts the reaction towards e) Removing H_2O(l) as it forms shifts the reaction towards products In which of the following reactions does the H_2PO^-_4 ion act as an acid? a) H_3PO_4 + H_2O rightarrow H_3O^+ + H_2PO^-_4 b) H_2PO^-_4 + H_2O rightarrow H_3O^+ + HPO^2-_4 c) H_2PO^-_4 + OH6- rightarrow H_3PO_4 + O^2- d) The ion cannot act as an acid. e) Two of these. For weak acid, HA, K_A = 7.3 times 10^-6. Calculate the pH of a 0.59 M solution of HA. a) 0.23 b) 2.68 c) 5.37 d) 11.32 e) none of these

Explanation / Answer

Q5

k = 2.2*10^-2 1/s

then

inintially, A0 = 1 M

find A at t = 205 s

apply first rate law

ln(A) = ln(A0) - kt

substitute data

ln(A) = ln(1) - (2.2*10^-2)*(205)

A = exp(-4.51)

A = 0.01099 M

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