MCAT General Chemistry Question 185: Answer and Explanation
Home > MCAT Test > MCAT general chemistry practice tests
Test Information
- Use your browser's back button to return to your test results.
- Do more MCAT general chemistry practice tests.
Question: 185
5. Given the standard enthalpies of formation (∆Hf˚) at 298 K for the compounds below, all of the following reactions are exothermic EXCEPT:
| Compound | ∆Hf° (kJ/mol) |
| C2H5OH(l) | –238.86 |
| CH3CHO(l) | –77.80 |
| CH3COOH(l) | –484.50 |
| H2O(l) | –285.83 |
- A. Yellow, indicating a lesser wavelength than ultraviolet light
- B. Yellow, indicating a greater wavelength than ultraviolet light
- C. Blue, indicating a lesser wavelength than ultraviolet light
- D. Blue, indicating a greater wavelength than ultraviolet light
Correct Answer: B
Explanation:
B All visible light has a greater wavelength than ultraviolet, eliminating choices A and C. The sodium lamp glows yellow and would therefore emit a yellow band on a dark background. If the question asked where dark bands would have been in an absorption spectrum, several lines would be seen in regions other than yellow since those colors are absorbed.