Question

1.05 - test review - counting atoms
how many total atoms are in one molecule of lactic acid?
hc₃h₅o₃

Explanation:

Step1: Identify each atom's count

In the formula $HC_3H_6O_3$ (note: this can also be written as $C_3H_6O_3H$ or simplified to $C_3H_7O_3$? Wait, no, original is $HC_3H_6O_3$ which is $H + C_3 + H_6 + O_3$. Wait, actually, the correct way is to sum the subscripts for each element. Let's parse the formula: $H$ (1), $C_3$ (3), $H_6$ (6), $O_3$ (3). Wait, no, actually, the formula is $HC_3H_6O_3$, so combining the H atoms: 1 (from first H) + 6 (from $H_6$) = 7 H atoms? Wait, no, maybe it's a typo and should be $C_3H_6O_3$ (lactic acid is $C_3H_6O_3$? Wait, no, lactic acid is $C_3H_6O_3$? Wait, no, lactic acid is $C_3H_6O_3$? Wait, molecular formula of lactic acid is $C_3H_6O_3$? Wait, no, let's check: lactic acid is 2 - hydroxypropanoic acid, formula $C_3H_6O_3$? Wait, no, $C_3H_6O_3$: C:3, H:6, O:3. Wait, but the given formula is $HC_3H_6O_3$, which would be H (1) + C (3) + H (6) + O (3). So total H: 1 + 6 = 7? Wait, that can't be. Wait, maybe the formula is written incorrectly, and it's $C_3H_6O_3$ (lactic acid's molecular formula is $C_3H_6O_3$? Wait, no, lactic acid is $C_3H_6O_3$? Wait, no, let's calculate: C:3, H:6, O:3. Sum: 3 + 6 + 3 = 12? Wait, no, if the formula is $HC_3H_6O_3$, then H:1 + 6 =7, C:3, O:3. Sum:7 +3 +3=13? Wait, that's a problem. Wait, maybe the formula is $C_3H_6O_3$ (correct lactic acid formula is $C_3H_6O_3$? Wait, no, lactic acid is $C_3H_6O_3$? Wait, no, let's check the structure: lactic acid is CH₃CH(OH)COOH, so formula is C₃H₆O₃. So C:3, H:6, O:3. So total atoms: 3 + 6 + 3 = 12. Wait, but the given formula is $HC_3H_6O_3$, which is H + C₃ + H₆ + O₃. So H:1 +6=7, C:3, O:3. 7+3+3=13. But that's conflicting. Wait, maybe the formula is written as $H C_3 H_6 O_3$, which is H (1), C (3), H (6), O (3). So total H:1+6=7, C:3, O:3. So sum:7+3+3=13. Wait, but maybe it's a typo and the formula is $C_3H_6O_3$ (lactic acid), which is 3 C, 6 H, 3 O. So 3+6+3=12. But the given formula has an extra H. Wait, maybe the user made a typo, but let's go with the given formula: $HC_3H_6O_3$. So:

• H atoms: 1 (from first H) + 6 (from $H_6$) = 7
• C atoms: 3 (from $C_3$)
• O atoms: 3 (from $O_3$)

Step2: Sum the counts

Total atoms = H + C + O = 7 + 3 + 3 = 13. Wait, but that seems odd. Wait, maybe the formula is $C_3H_6O_3$ (lactic acid), which is 3 C, 6 H, 3 O. So 3+6+3=12. But the given formula has an extra H. Wait, maybe the formula is written as $H C_3 H_6 O_3$ which is the same as $C_3 H_7 O_3$? No, that's not lactic acid. Wait, maybe the user made a mistake, but let's proceed with the given formula.

Wait, let's re-express the formula: $HC_3H_6O_3$ can be rewritten by combining the H terms: $H^{1}C^{3}H^{6}O^{3}$ = $C^{3}H^{1 + 6}O^{3}$ = $C_3H_7O_3$. So H:7, C:3, O:3. Total atoms:7 + 3 + 3 = 13.

But wait, lactic acid's formula is $C_3H_6O_3$, so maybe the given formula has a typo (extra H). But according to the given formula, we have to go with that.

So step by step:

1. Identify each element and its subscript:

• H: 1 (from the first H) + 6 (from $H_6$) = 7
• C: 3 (from $C_3$)
• O: 3 (from $O_3$)

1. Sum the number of each atom: 7 (H) + 3 (C) + 3 (O) = 13.

Answer:

13