How many valence electrons are in a molecule of formaldehyde (CH2O)? Point A: 010 Point B: 016 Point C: 08 How many valence electrons are in a polyatomic ion of formate (CH3O-)? Point A: 010
The Correct Answer and Explanation is:
Correct Answers:
Question 44:
How many valence electrons are in a molecule of formaldehyde (CH₂O)?
✅ Correct answer: 12
Explanation:
To calculate the total number of valence electrons in formaldehyde (CH₂O), count the valence electrons of each atom:
- Carbon (C): 4 valence electrons
- Hydrogen (H): 1 valence electron × 2 = 2
- Oxygen (O): 6 valence electrons
Total = 4 (C) + 2 (H) + 6 (O) = 12 valence electrons
Question 45:
How many valence electrons are in a molecule of formate ion (CH₃O⁻)?
✅ Correct answer: 18
However, none of the options in your screenshot are correct for CH₃O⁻. Let’s see why:
Explanation:
- Carbon (C): 4 valence electrons
- Hydrogen (H): 1 × 3 = 3 valence electrons
- Oxygen (O): 6 valence electrons
- Extra electron (⁻ charge): 1 additional electron
Total = 4 (C) + 3 (H) + 6 (O) + 1 (charge) = 14 valence electrons
⚠️ The correct total for CH₃O⁻ (formate ion with one hydrogen on carbon) is 14 valence electrons, not 8, 10, 12, or 16 as listed in the options.
There may be confusion with formic acid (HCOOH) or formate ion (HCOO⁻) which contains 18 valence electrons. That structure is:
- 1 Carbon (4)
- 1 Hydrogen (1)
- 2 Oxygen (6×2 = 12)
- 1 extra electron for the negative charge (1)
Total = 4 + 1 + 12 + 1 = 18
So if the question meant HCOO⁻ (formate ion), the correct number of valence electrons is 18.
Summary:
- CH₂O (formaldehyde): 12 valence electrons
- CH₃O⁻ (methoxide ion): 14 valence electrons
- HCOO⁻ (formate ion): 18 valence electrons
The image shows correct choice for CH₂O but incorrect or unclear options for the ion.
