AAMC 8, gen chem question 40

[MedGrl@2022]

Hi I have a question about passage VI. Basically in this passage a mixture of NiSO4, H2O and Na2CO3 were mixed together and a green precipitate forms. After dividing the slurry into two equal portions an excess of 6M HCl was added.

Question 40 asks:

According to the information in the passage, the gas that evolves is:

A) sulfur dioxide
B) sulfur trioxide
C) carbon dioxide
D) carbon monoxide

The answer is C (Carbon Dioxide). AAMC states that according to the passage, the gas is given off when HCl is added to one portion of the slurry. HCl is added to one portion of the slurry. HCl reacts with CO3(2-) to form CO2(g). Thus, C is the best answer.

I guessed this answer correctly but I am still unsure about how I should know this for sure. Why aren't the other ones possibilities? Should I know this because it is similar to the bicarbonate reaction that happens near our aveloi to release CO2 from our bodies?

Thank you for all your help.

Verónica

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[Postictal Raiden]

Hi I have a question about passage VI. Basically in this passage a mixture of NiSO4, H2O and Na2CO3 were mixed together and a green precipitate forms. After dividing the slurry into two equal portions an excess of 6M HCl was added.

Question 40 asks:

According to the information in the passage, the gas that evolves is:

A) sulfur dioxide
B) sulfur trioxide
C) carbon dioxide
D) carbon monoxide

The answer is C (Carbon Dioxide). AAMC states that according to the passage, the gas is given off when HCl is added to one portion of the slurry. HCl is added to one portion of the slurry. HCl reacts with CO3(2-) to form CO2(g). Thus, C is the best answer.

I guessed this answer correctly but I am still unsure about how I should know this for sure. Why aren't the other ones possibilities? Should I know this because it is similar to the bicarbonate reaction that happens near our aveloi to release CO2 from our bodies?

Thank you for all your help.

Verónica

NiSO4 + Na2CO3 = Na2SO4 aq + NiCO3 green ppt

Once HCl is added, it will react with NiCO3 and produces CO2. How do we know that it reacted with NiCO3 and not with SO4 2-? because the passage says the ppt disappeared. So, now you could at least eliminate options A and B since HCl didn't react with Na2SO4. To decide whether it's C and D you could either take a leap of faith and go with C since D is a toxic gas and it's unlikely that the passage will not mention that the gas formed was toxic, so people don't go ahead and do the experiment, someone dies and sue AAMC (I know, too many speculations). Or do the following:

2HCl + Na2CO3 = H2O + CO2 + 2NaCl

 

[MedGrl@2022]

NiSO4 + Na2CO3 = Na2SO4 aq + NiCO3 green ppt

Once HCl is added, it will react with NiCO3 and produces CO2. How do we know that it reacted with NiCO3 and not with SO4 2-? because the passage says the ppt disappeared. So, now you could at least eliminate options A and B since HCl didn't react with Na2SO4. To decide whether it's C and D you could either take a leap of faith and go with C since D is a toxic gas and it's unlikely that the passage will not mention that the gas formed was toxic, so people don't go ahead and do the experiment, someone dies and sue AAMC (I know, too many speculations). Or do the following:

2HCl + Na2CO3 = H2O + CO2 + 2NaCl

Awesome! Thank you! And I know that the participate was NiCO3 because the partially filled d orbitals of Ni are responsible for the green color of the precipitate. Right?

 

[Postictal Raiden]

Awesome! Thank you! And I know that the participate was NiCO3 because the partially filled d orbitals of Ni are responsible for the green color of the precipitate. Right?

I know that NiCO3 is the ppt because carbonates are insoluble unless combined with elements from the first group of the periodic table (the case of Na2CO3). In regards to color change and d oribitals, I will let someone else comment since this is my weakness in gChem.

 

[adrakdavra]

someone dies and sue AAMC? is this even possible

so people don't go ahead and do the experiment, if they do what is going to happen CO ??

 

[HotHamH2O]

I know that NiCO3 is the ppt because carbonates are insoluble unless combined with elements from the first group of the periodic table (the case of Na2CO3). In regards to color change and d oribitals, I will let someone else comment since this is my weakness in gChem.

When the d-level is not completely filled, it is possible to promote and electron from a lower energy d-orbital to a higher energy d-orbital by absorption of a photon of electromagnetic radiation having an appropriate energy.

So if you shine white light on a complex (white light has all colors), one will be absorbed by the complex. Which? - the one that corresponds to energy gap between split d orbitals, The complex will have complementary color to the one that is being absorbed.