I know there is alot of questions but any help would be appreciated Thank You!!!
ID: 824727 • Letter: I
Question
I know there is alot of questions but any help would be appreciated Thank You!!!!!!!
1. what is the pH of a mixture containing 0.30 M HNO2 and 0.15 M NaNO2 (Ka for NO2 = 4.5x10^-4)?
(answers 3.05, 4.05, 4.35, 4.65, 5.01)
2. Which of the following combinations would be the best to buffer the pH to 9.0?
(answers: H3PO4 and H2PO4- ka = 7.5x10^-3, HNO2 and NO2- ka= 4.5x10^-4, CH3CO2H and CH3COO- ka=1.8x10^-5, H2PO4- and HPO42- ka=6.2x10^-8, NH4+ and NH3 ka=5.7x10^-10)
3. what is the pH of a buffer that results when 0.50 mole of H3PO4 is mixed with 0.75 mole NaOH and diluted with water to 1.00 L (ka1=7.5x10^-3, ka2=6.2x10^-8, ka3=3.6x10^-13)?
(answers: 7.21, 7.45, 8.01, 8.23, 9.91)
4. A buffer contains 0.50 mol CH3CO2H and 0.50 mol CH3CO2- diluted with water to 1.0L. How many moles of NaOH are required to increase the pH of the buffer to 5.00 (pka=CH3CO2H=4.74)
(answers: 0.12, 0.15, 0.17, 0.26, 0.35)
5. Which one of the following conditions is met at the equivalence point of the titration of a monoprotic weak acid with a strong base?
answers:
a) the volume of base added from the buret must equal the volume of acid titrated
b) the moles of base added from the buret equal the initial moles of acid
c) the molarity of the base equal the initial molarity of the weak acid
d) the percent ionization of the base must equal the percent ionization of the acid
e) the pH of the solution is equal to or less than 7.00
6. Sodium Hydroxide is used to titrate 50.0 mL of 0.100 M Benzoic acid. What is the pH after the addition of 50 mL of 0.200 M NaOH (ka for benzoic acid = 6.3x10^-5)?
7. what is the solubility product for Ca(IO3)2
8. the ksp for BaF2 is 1.7x10^-6. What is the concentration of Ba2+ in a saturated solution of BaF2?
9. Calculate the molar solubility of CaCO3 in 0.50 M CaCl2. The ksp for CaCO3 is 3.8x10^-9. Assume that CO32- does not react aprreciably with water
10. only 1.06g of Ca(NO3)2 will dissolve per liter of a solution that is buffered to a pH of 13.00. What is the value of ksp for Ca(OH)2? Molar mass of Ca(NO3)2 is 164.1 g/mol
11. What mass of Na2SO4 (molar mass=1442.0 g/mol) must be added to 225ml of 0.33 M Ag+ to initiate precipitation of Ag2SO4? the ksp for Ag2SO4 is 1.7x10^-5. Assume no volume change occurs upon addition of Na2SO4
12. what is the expression of the rate reaction of NO(g) and Cl(g)
2 NOCl (g) -> 2 NO(g) + Cl2(g)
13. Given the initial rate data for the reaction A + B ---> C determine the rate expression for the reaction
[A],M [B], M delta [C]/delta t (initial) M/s
0.25 0.15 1.23x10^-3
0.25 0.25 3.42x10^-3
0.25 0.15 2.46x10^-3
Explanation / Answer
1.Use Henderson - Hasselbalch equation:
pH = pKa + log ([salt] / [acid])
pKa HNO2 = -log 4.5*10^-4 = 3.35
pH = 3.35 + log (0.15/0.30)
pH 3.35 + log 0.5
pH = 3.35 + (-0.30)
pH = 3.05
2.NH4+ and NH3 ka=5.7x10^-10
ph = pka+log(cbase/acid)
= 9.24+ log(0.23/0.1) = 9.61
3. 1.5 equivalents of naoh added generates equimolar nah2po4 and na2hpo4
ph = pka2 = -log(6.2*10^-8) = 7.21
4.pH = pKa + log [CH3COO-] / [CH3COOH]
5.24 = 4.74 + log [CH3COO-] / [CH3COOH]
5.24 - 4.74 =0.50
10^0.50= 3.16 = [CH3COO-] / [CH3COOH]
initial concentration CH3COOH = initial concentration CH3COO- = 0.50 mol/ 1.0 L = 0.50 M
3.16 = 0.50+x / 0.50-x
1.58 - 3.16 x = 0.50+x
1.08 = 4.16 x
x = 0.260 = moles NaOH required