12 4. which of the followings are true about pH, pOH, and Kw? ultiple-Answer A.
ID: 1075151 • Letter: 1
Question
12 4. which of the followings are true about pH, pOH, and Kw? ultiple-Answer A. Pure water at 25 degree and 1 atmosphere pressure is barely ionized B. The higher of the pH, the higher concentration of hydrogen ion C. The higher of the pOH, the higher concentration of hydrogen ion D. For aqueous solution at specific temperature and atmosphere pressure, the Kw for H20 is a constant E. The unit of Kw is M not M square Multiple_Choice 5.Which of the followings are true in aqueous solution (this is basically a mathematical issue)? A. 0.1 M HCI has a pH-1 B. 0.1 M acetic acid has a pH more than 1 (need to think) C. 0.1 M NaOH has a pH 1 D. 0.2 M HCI has a higher pH than 0.1 M HCI Multiple_Choice 6. Which of the following has the strongest buffering capacity? A. H2O B. 0.1 M HCI C. 0.1 M carbonic/bicarbonate (H2CO3/HCO3-) at pH pKa D. 0.2 M carbonic/bicarbonate (H2CO3/HCO3-) at pH pKaExplanation / Answer
4) The ionization of water at 25°C is given as
H2O (l) <=====> H+ (aq) + OH- (aq)
The ionization constant is given as
Kw = [H+][OH-] = 1.0*10-14 mol2dm-6 at 25°C.
Kw is the equilibrium constant for the ionization reaction. The value of Kw is quite small (of the order of 10-14) and hence, the extent of ionization, i.e, the extent to which H2O splits up to give H+ and OH- must be small. Therefore, pure water is almost unionized at 25°C and hence, statement (a) is true.
The pH of a solution is defined as pH = -log [H+]; therefore, [H+] = antilog (-pH). Therefore, the higher the pH of the solution, the lower is the value of the antilog and hence, the lower is [H+]. Therefore, statement (b) is false.
The pOH of a solution is defined as pOH = -log [OH-].
The pH and pOH of a solution are related as pH + pOH = 14.
Therefore, the higher the pOH of a solution, the lower is the value of pH. Again, we have defined [H+] as the antilog of –pH; hence, the lower the pH, the higher is the value of the antilog and consequently, higher is pH. Therefore, statement (c) is true.
Kw has been defined as equilibrium constant and hence, Kw depends on the temperature of the reaction. Hence, statement (d) is true.
We have already defined the unit of Kw above. Since the equilibrium constant has unit mol2dm-6, hence, there must be a M2 in the unit. Therefore, statement (e) is false.
Related Questions
Navigate
Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.