Question

29 multiple choice 1 point
what is the balancing coefficient of water, h₂o, in the following chemical equation?
c₃h₈ + 5o₂ ⟶ 4h₂o + 3co₂ + energy
5
4
1
3
clear my selection
30 multiple choice 1 point
which equation is properly balanced?
2fe + 3o₂ →4 fe₂o₃
2fe + 2o₂ →2 fe₂o₃
fe + o₂ → fe₂o₃
4fe + 3o₂ →2 fe₂o₃
clear my selection

Explanation:

Question 29

Step1: Identify the coefficient of \(H_2O\)

In the given chemical equation \(C_3H_8 + 5O_2
ightarrow 4H_2O + 3CO_2 + \text{energy}\) (note: the original reactant should be \(C_3H_8\) not \(C_3H_3\) for a valid combustion reaction), the coefficient in front of \(H_2O\) is 4.

Step1: Check Fe and O atoms for each option

• Option 1: \(2Fe + 3O_2

ightarrow 4Fe_2O_3\)
Fe: Left = 2, Right = \(4\times2 = 8\) (unbalanced).
O: Left = \(3\times2 = 6\), Right = \(4\times3 = 12\) (unbalanced).

• Option 2: \(2Fe + 2O_2

ightarrow 2Fe_2O_3\)
Fe: Left = 2, Right = \(2\times2 = 4\) (unbalanced).
O: Left = \(2\times2 = 4\), Right = \(2\times3 = 6\) (unbalanced).

• Option 3: \(Fe + O_2

ightarrow Fe_2O_3\)
Fe: Left = 1, Right = 2 (unbalanced).
O: Left = 2, Right = 3 (unbalanced).

• Option 4: \(4Fe + 3O_2

ightarrow 2Fe_2O_3\)
Fe: Left = 4, Right = \(2\times2 = 4\) (balanced).
O: Left = \(3\times2 = 6\), Right = \(2\times3 = 6\) (balanced).

Answer:

B. 4

Question 30