5. Para la siguiente reacción: KClO3 (s) KCl(s) + O2 Si se descomponen 500 gramos de una muestra impura de clorato de potasio y se recogen 100 litros de O2 medidos bajo condiciones normales de presión y temperatura. Determine la pureza de la muestra.

72.95%

Explanation:

Para resolver esta pregunta, debemos hallar las moles tóricas que se producirían en la reacción asumiendo que los 500g son únicamente de clorato de potasio haciendo uso de la reacción balanceada:

2KClO₃(s) → 2KCl(s) + 3O₂(g)

Donde dos moles de clorato de potasio producen tres moles de oxígeno.

Después de hallar las moles teóricas de oxígeno debemos hallar las moles producidas usando PV = nRT. La pureza SERÁ:

Moles producidas / moles Teóricas * 100

Moles clorato -Masa molar: 122.55g/mol-:

500g KClO₃ * (1mol / 122.55g) = 4.08 moles KClO₃

Moles O₂ teóricas:

4.08 moles KClO₃ * (3 moles O₂ / 2 moles KClO₃) = 6.12 moles

Moles producidas:

PV / RT = n

Donde P = 1atm a STP

V es volumen = 100L

R es constante de los gases = 0.082atmL/molK

T =273.15K a STP

Reemplazando:

1atm*100L / 0.082atmL/molK*273.15K = 4.46 moles

La pureza de la muestra es:

4.46 moles / 6.12 moles * 100 = 72.95%

1. the question asks the most appropriate, which seems to rule out "all of the above." your choice appears to be the correct one.

2. the protocol described is good for identifying correlation, but not cause and effect. for cause/effect, you need to devise a protocol that will assign the treatment (or not) to groups that have essentially the same "demographics" with respect to all the other variables. your choice regarding control group seems appropriate. random assignment of treatment (choice d) may be appropriate also. (i think you can argue that b and d are just different descriptions of the same method.)

3. d will randomize the birds, but may not guarantee there are 10 in each group. e will do both, so seems the better choice.

comment on question 2

based on the problem statement, it seems clear that confident, attentive drivers are more likely to use daytime running lights. so, the protocol might need to be devised in such a way that the lights would be turned on or off without the driver's knowledge. (an attentive driver will figure it out.) assigning a confident, attentive driver to a group required to drive without running lights might mess with his/her confidence and attentiveness. you don't want your experiment to do that. (nor do you want the experiment to subject a driver to greater risk of accident as a consequence of driving without running lights.) experiments involving human safety are always problematic.