AP Chem Help #2?

Question

At elevated temperatures, sodium chlorate decomposes to produce sodium chloride and oxygen gas. A 0.8935 g sample of impure sodium chlorate was heated until the production of oxygen gas ceased. The oxygen gas collected over water occupied 57.2 mL at a temperature of 22°C and a pressure of 746 torr. Calculate the mass percent of NaClO3 in the original sample. (At 22°C the vapor pressure of water is 19.8 torr.)



Please explain tooo. THANKS ! :D

Answer 1

2 NaClO3 = 2 NaCl + 3 O2

p×V = n×R×T
p = 746 - 19.8* torr = 726.2 torr = 96,82 kPa
V = 57.2 ml = 57.2 cm3 = 0.0572 dm3
R = 8.314 dm3×kPa/K×mol
T = 22°C = 273+22 K = 295 K

n = (p×V)/(R×T) = 96.82×0.0572/8.314×295 = 0.002258 mol O2

1 mol NaClO3 --> 106.5 g/mol

2×106.5 g NaClO3 --> 3 mol O2
? g ------------------------> 0.002258 mol O2
0.1603 g NaClO3 --> 0.002258 O2

0.8935 g -- 100%
0.1603 g -- (17,94 %)

I'm afraid there is a mistake somewhere (in my calculation or in the question, this is a very very impure NaClO3)

* the vapor pressure must be subtract form the whole pressure

Answer 2

Subtract vapour pressure of water. Then use

PV = nRT

to find moles O2. (Care with units!)

Use balanced equation to find moles NaClO3. Multiply by formula weight to find g NaClO3. There you are!

Answer 3

i prefer to preface my answer by ability of way of telling u that u can digital mail me with the numerous questions. it fairly is puzzling to respond to all 3 questions, yet ill attempt. a million. we see that H3O+ is the foremost effectual acid, by using actuality water is an extremely very vulnerable base. thye conjugate of a good acid is a vulnerable base. the extra ideal the acid, the weaker its conjugate. the extra ideal the backside, the weaker its conjugate. 2. i be attentive to for exceptionally much particular that B(OH)3 is an ACID. in optimal situations, all nonmetal OH's are acids. if u rearrange this formulation, u get H3BO3. i pass to declare D. 3. to locate the pH of a vulnerable acid, u take the sq. root of Ka x Molarity. thinking all molarities are a million, take the sq. root of each and every of the Ka's and take the detrimental log of what u have been given. and the closest one to 7 is the winner. it is going to be the NH4+ i'm hoping this helps.