I need help with chemical homework.. I need to determine how many atoms are in each question...using the rules of cofficients and subscripts?

Number of atoms = Coefficient × (Sum of subscripts)
(Note that the subscript "1" is not shown.)

1.
No. of atoms in 3CO₂ = 3 × (1 + 2) = 9

2.
No. of atoms in 5C₂H₄O = 5 × (2 + 4 + 1) = 35

3.
No. of atoms in 2H₂CO₃ = 2 × (2 + 1 + 3) = 12

4.
(CAO3 does not exist. It may be CaCO₃.)
No. of atoms in 7CaCO₃ = 7 × (1 + 1 + 3) = 35

5.
No. of atoms in 1CaCl₂ = 1 × (1 + 2) = 3

6.
No. of atoms in 6PbSO₄ = 6 × (1 + 1 + 4) = 36

"I took this class a few months ago and a year ago"

I won't tell you exactly when I took chemistry but the word 'hippie' was used a lot about that time.

Mackenzie messed up alto!!

3co2 ---> 3 C and 6 O (not 6 CO)

My 2nd is 5C2H4O: 5 O, 10 C, 20 H (5 x 4 for the H)

MY 3RD IS : 2H2CO3 4 H, and either 6 CO or 3 C 6 O <--- it's 2 C and 6 O, the 4 H is correct

MY 4TH IS : 7CAO3 ---> 7Ca (the CA should be Ca) and 21 O (BTW, CAO3 is not a compound that exists)

one Ca and 2 Cl ---> not CL

MY 6TH IS: 6PbSO4 6 Pb 6 S 24 O <--- the only one that is correct

Not certain, but:
My 1st is 3co2? 6 CO

My 2nd is 5C2H4O: 5 O, 10 C, 8 H

MY 3RD IS : 2H2CO3 4 H, and either 6 CO or 3 C 6 O

MY 4TH IS : 7CAO3 7 C 7 A 21 O

MY 5TH IS: 1CACL2 1 C 1 A 2 CL

MY 6TH IS: 6PbSO4 6 Pb 6 S 24 O

Try this! Not too reliant, but it might be correct xD I took this class a few months ago and a year ago