Chem Help Please

[Fez]

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Hello, I'm new in the forum as a registered user but I have been reading it for a while now.

I need help with some chemistry problems I don't know that to do. I have been looking for help but nobody seems able to help me.

These are the problems I hope you can help me.

1. What will happen to the temperature of the system at equilibrium, shown below, as SO2 is added to the system

Heat + SO2Cl2 (g) ↔ SO2 (g) + Cl2 (g): *

a.temperature will increase​

b.temperature will decrease​

c.temperature is not changed​

d.cannot be determined based on information provided​

Please respond to the question above.​

2. The first-order rate constant for the decay of the radioactive isotope tritium is 0.056 year-1. What fraction of the tritium initially in a sample is still present 50 years later?: *

a. 0.061​

b. 0.25​

c. 0.75​

d. 0.94​

Please respond to the question above.​

3. What is the pH of a 0.075 M triethylamine solution? [Kb for (C2H5)3N = 5.3 × 10-4].: *

a.2.20​

b.4.80​

c.9.20​

4. In a laboratory experiment, 10.8 g copper (II) chloride was reacted with 18.4 g sodium nitrate. The actual yield of sodium chloride was 6.2g. What was the percent yield?: *

a.44%​

b.49%​

c.51%​

d.66%​

Please respond to the question above.​

d.11.80​

​

I hope you can help with these problems

Thanks in advance
​

Please respond to the question above.​

 

[Chemboy23]

1.) When you add a product (SO2) in this case, you shift the equilibrium to the left (refer to Le Chatelier's principle)...meaning as you add more product, nature will counterbalance it and cause an increase on the left side (the reactants). Always remember, you want everything to balance, so when you add to one side, mother nature adds to the other, really cool in my opinion. Anyway, in the scenario, you have an endothermic reaction (heat is the reactant), so if you increased the concentation of a product (on right), mother nature would cause all of the reactants (left side) to increase. Heat is a reactant, thus an increase in heat would be observed. Correct answer choice is A 😀

2.) Start with 0.056g (I assume that's the metric here (grams)).

Step 1) fraction of nuclei remaining = (1/2)^n
***n=number of half lives gone by when you hit 50 years

(0.056)^50=~2.57 ---so this means that after 50 1/2 lives, you have this much remaining...So answer choice B is the best fit here.

3.) I'll give you the way to follow. First calculate pOH and after pH =14- pOH

pKb = log 1/5.3*10^-4=3.28

pOH= (pKb-log of conc.)/2= (3.28-log 0.075)/2=2.20

formula pH=14-pOH= 14-2.20= 11.8 - Answer choice D

4.) So, let's get the formula. %Yield=Actual/Theoretical x 100...

Now, we have the "actual" from the experiment, we need to calculate what we "should" get if everything was perfect. Most of the time, this requires a little stochiometry and such...so, here it goes. Convert everything to moles and start with the lowest number (the limiting reagent).

10.8 g CuCl2 x 1 mol CuCl2 = 0.08 moles of CuCl2
134.4 g CuCl2

18.4 g NaNO3 x 1 mol NaNO3 = 0.22 moles of NaNO3
85 g NaNO3

So, pay attention, use the limiting reagent (in this case CuCl2) to start your stochiometry.

Like this.

Overall Eqn. CuCl2 + 2NaNO3 -----> 2NaCl + Cu(NO3)2 ---make sure to balance everything!!! VERY IMPORTANT

Now, off to the end.

0.08 mol CuCl2 x 2 mol NaCl x 58.45 g NaCl = 9.35 g NaCl
1 mol CuCl2 1 mol NaCl

We would have gotten 9.35 g if lab conditions were PERFECT, but they're not...so we only got 6.2g

So...finally...Percent Yield = 6.2 g NaCl x 100 = 66.3%---Answer D
9.35 g NaCl

Just think about it this way, you lost ~33.7% of your product to the atmosphere as waste (in some way or another) and you only gained 66.3% of what you would expect under "perfect" conditions.

Hope this helps!!!

Best of luck to you my friend