How to Solve These Chemistry Exam Questions?

[g-funk]

hi guys
these were some questions i got wrong in a an exam, i was unable to attend the lecture following the exam so i am not sure how to do these two questions that i got wrong i have working, although it is to complicated to put on htis site if anyone can ghet an answer, that would be great then i might know were i went wrong in my working out. cheers

Question 12

A current of 3.97 A is passed through an electrolytic cell containing a dilute sulfuric acid solution for 3.66 hours. Calculate the total volume of gases (in L) generated at 0oC and 100 kPa.
Do not use scientific notation for your answer
R = 8.314 kPa L mol-1K-1 and F = 96480 C mol-1





Question 13 (1.0 points)

Technetium-99( atomic mass 98.9 daltons) is used for bone scans. It has a half-life of 6.0 hours. How many disintegrations can you expect from 60.46 mg technetium-99 in 1 second? (Answer to 3 significant figures and use form eg. 1.10e15 for 1.10 x 1015)

 

[Gokul43201]

The working is not too complicated to write down. If you think it is, then say what steps you took, and what final answer you got.

We can not respond until we see some work from you.

 

[ravenprp]

Hi there,

I'm sorry to hear that you got these questions wrong on your exam. It can be frustrating when we don't understand how to solve certain problems. I'll do my best to explain the solutions to these questions.

Question 12:

To solve this question, we need to use the formula Q = It, where Q is the charge in coulombs, I is the current in amperes, and t is the time in seconds. Since we are given the current and time, we can calculate the charge as follows:

Q = (3.97 A)(3.66 hours)(3600 seconds/hour) = 52,451.2 C

Next, we need to use the formula PV = nRT to calculate the volume of gas generated. We are given the pressure (100 kPa), temperature (0oC = 273 K), and the gas constant (R = 8.314 kPa L mol-1K-1). We can also find the number of moles of gas (n) using the formula n = Q/F, where Q is the charge we calculated earlier and F is the Faraday constant (96480 C mol-1). Therefore:

n = (52,451.2 C)/(96480 C mol-1) = 0.5435 mol

Now, we can plug all of this information into the PV = nRT equation and solve for V (volume):

V = (0.5435 mol)(8.314 kPa L mol-1K-1)(273 K)/(100 kPa) = 11.13 L

So, the total volume of gas generated is 11.13 L.

Question 13:

To solve this question, we need to use the equation N = N0(e^-λt), where N is the final number of disintegrations, N0 is the initial number of disintegrations, λ is the decay constant (ln2/t1/2), and t is the time in seconds. We are given the half-life of technetium-99 (6.0 hours = 21600 seconds) and the amount of technetium-99 (60.46 mg). We can find N0 by converting the mass to moles and then using Avogadro's number:

N0 = (60.46 mg)/(98.9 g/mol)/(6.022x10^23 particles/mol) = 9