1.which one of the following will give a solution with a pH >7, but is not an Ar

Question

1.which one of the following will give a solution with a pH >7, but is not an Arrhenius base in the strict sense?

a) CH3NH2

b)NaOH

c)CO2

d)Ca(OH)2

e)CH4

when the temperature of a sample of pure water is raised above 25 C (CELCIOUS) ,

a) the hydronium ion concentration will be greater thatn the hydroxide ion concentration.

b) the hydronium ion concentration will be les than the hydroxide ion concentration.

c) the value of Kw will increase.

d) the hydronium ion concentration could change to 1.0*10^-10 M

e)  the hydroxide ion concentration could change to 1.0*10^-10 M

4. when 14.7 mL of aqueous HBr (a strong acid) was added to water, 0.482L of a sol'n with a pH of 4.23 was produced. What was the molarity of the original HBr sol'n?

answer ) 1.9 *10-3

5. Accoring to Bronsted and Lowry, which one of the following is not a conjugate acid-base pair?

a) H3O+ / OH-

b) CH3OH2+   / CH3OH

c) HI / I-

d) HSO4 / SO42-

e) H2 / H-

I already knew these answers, but I don't know the resaon ..

Please explain the questions to me! Thanks!

1.which one of the following will give a solution with a pH >7, but is not an Arrhenius base in the strict sense? a) CH3NH2 b)NaOH c)CO2 d)Ca(OH)2 e)CH4 2. Given : when the temperature of a sample of pure water is raised above 25 C (CELCIOUS) , a) the hydronium ion concentration will be greater thatn the hydroxide ion concentration. b) the hydronium ion concentration will be les than the hydroxide ion concentration. c) the value of Kw will increase. d) the hydronium ion concentration could change to 1.0*10^-10 M e) the hydroxide ion concentration could change to 1.0*10^-10 M 4. when 14.7 mL of aqueous HBr (a strong acid) was added to water, 0.482L of a sol'n with a pH of 4.23 was produced. What was the molarity of the original HBr sol'n? answer ) 1.9 *10-3 5. Accoring to Bronsted and Lowry, which one of the following is not a conjugate acid-base pair? I already knew these answers, but I don't know the resaon .. Please explain the questions to me! Thanks!

Explanation / Answer

1) CH3NH2 + H2O ----> CH3NH3+ + OH-   (this will increase the amount of OH-) and this is not a strict Arrhenius base.

2) kw will increase. When the temperature rise the autonionization of water makes pKw decrease, therefore, as it is a logarithmic function, kw wil increase.

3) When you have an strong acid, you can despise the water contribution to pH. So, you can obtain the [H3O+] value direct from the pH:

[H3O+] = 10-4.23 = 5.89 E-5 M

Now, let's calculate the moles in solution:

moles H3O + = 5.89 E-5 moles/ L * 0.482 L = 2.84 E-5 moles

Now, moles of H3O+ = moles H+ given by the strong acid, so, you can have the initial molarity of the HBr by:

[HBr] = 2.84E-5 moles / 0.0147 L = 1.93 E-3 M

5) It'll be e) H3O/OH- because one can't turn into the other when accepting or giving electrons. If OH- receive a proton, it turns into H2O not H3O. Same for the H3O; if it give a proton, it'll turn into H2O, not OH-.

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