Question

directions for each problem:

1. recognize and record individual elements
2. recognize the subscripts as the number of atoms for an element
3. recognize the coefficients as the number of atoms for all elements in the compound.
4. total all atoms for an element.

examples:
a) naoh
na - 1
o - 1
h - 1 3 total atoms
b) 5znso₄
zn - (5x1 = 5)
s - (5 x 1 = 5)
o - 20 (5 x 4 = 20) 30 total atoms

1. h₂o
2. mgcl₂
3. li₂so₄
4. nac₂h₃o₂
5. nh₄cl
6. hbr
7. 4hno₃
8. 4li₂o
9. 3h₂o
10. 3al₂o₃
11. 2ch₃oh
12. 2h₃nch₃br

Explanation:

Step1: Analyze H₂O

For H₂O, the coefficient is 1 (implicit). H has a sub - script of 2 and O has a sub - script of 1. So, H atoms = 2, O atoms = 1, total atoms = 3.

Step2: Analyze MgCl₂

For MgCl₂, the coefficient is 1. Mg has 1 atom and Cl has a sub - script of 2, so Cl atoms = 2, total atoms = 3.

Step3: Analyze Li₂SO₄

For Li₂SO₄, coefficient is 1. Li has 2 atoms, S has 1 atom, O has 4 atoms, total atoms = 7.

Step4: Analyze NaC₂H₃O₂

For NaC₂H₃O₂, coefficient is 1. Na has 1 atom, C has 2 atoms, H has 3 atoms, O has 2 atoms, total atoms = 8.

Step5: Analyze NH₄Cl

For NH₄Cl, coefficient is 1. N has 1 atom, H has 4 atoms, Cl has 1 atom, total atoms = 6.

Step6: Analyze HBr

For HBr, coefficient is 1. H has 1 atom, Br has 1 atom, total atoms = 2.

Step7: Analyze 4HNO₃

Coefficient is 4. N has 4 atoms, H has 4 atoms, O has 4×3 = 12 atoms, total atoms = 20.

Step8: Analyze 4Li₂O

Coefficient is 4. Li has 4×2 = 8 atoms, O has 4 atoms, total atoms = 12.

Step9: Analyze 3H₂O

Coefficient is 3. H has 3×2 = 6 atoms, O has 3 atoms, total atoms = 9.

Step10: Analyze 3Al₂O₃

Coefficient is 3. Al has 3×2 = 6 atoms, O has 3×3 = 9 atoms, total atoms = 15.

Step11: Analyze 2CH₃OH

Coefficient is 2. C has 2 atoms, H has 2×4 = 8 atoms, O has 2 atoms, total atoms = 12.

Step12: Analyze 2H₃NCH₃Br

Coefficient is 2. H has 2×6 = 12 atoms, N has 2 atoms, C has 2 atoms, Br has 2 atoms, total atoms = 18.

Answer:

1. H: 2, O: 1, total atoms: 3
2. Mg: 1, Cl: 2, total atoms: 3
3. Li: 2, S: 1, O: 4, total atoms: 7
4. Na: 1, C: 2, H: 3, O: 2, total atoms: 8
5. N: 1, H: 4, Cl: 1, total atoms: 6
6. H: 1, Br: 1, total atoms: 2
7. H: 4, N: 4, O: 12, total atoms: 20
8. Li: 8, O: 4, total atoms: 12
9. H: 6, O: 3, total atoms: 9
10. Al: 6, O: 9, total atoms: 15
11. C: 2, H: 8, O: 2, total atoms: 12
12. H: 12, N: 2, C: 2, Br: 2, total atoms: 18