Question

in the unbalanced chemical equation below, what series of numbers represent the coefficients needed to balance the chemical equation?
al + cl₂ → alcl₃
a 1, 2, 1
b 3, 5, 1
c 2, 3, 2
d 1, 1, 1

question 24
what is the empirical formula for c₂h₄?
a c₂h₂
b ch₂
c c₂h
d c₂h₄

question 25
in the unbalanced chemical equation below, select the series of numbers that represent the coefficients needed to balance the equation.
h₂ + o₂ → __h₂o
a 1, 1, 2
b 2, 1, 2
c 3, 2, 1
d 1, 1, 1

Explanation:

Question (Balancing \( \text{Al} + \text{Cl}_2

ightarrow \text{AlCl}_3 \))

Step1: Balance Chlorine atoms

On the right, \( \text{AlCl}_3 \) has 3 Cl atoms. On the left, \( \text{Cl}_2 \) has 2 Cl atoms. The least common multiple of 2 and 3 is 6. So, put coefficient 3 in front of \( \text{Cl}_2 \) (to get 6 Cl atoms) and coefficient 2 in front of \( \text{AlCl}_3 \) (to get 6 Cl atoms). Now the equation is: \( \text{Al} + 3\text{Cl}_2
ightarrow 2\text{AlCl}_3 \).

Step2: Balance Aluminum atoms

Now, on the right, \( 2\text{AlCl}_3 \) has 2 Al atoms. So put coefficient 2 in front of \( \text{Al} \) on the left. The balanced equation is: \( 2\text{Al} + 3\text{Cl}_2
ightarrow 2\text{AlCl}_3 \). The coefficients are 2, 3, 2.

The empirical formula is the simplest whole - number ratio of atoms in a compound. For \( \text{C}_2\text{H}_4 \), the ratio of C to H is \( 2:4 \). We can divide both numbers by their greatest common divisor, which is 2. So, \( \frac{2}{2}:\frac{4}{2}=1:2 \), and the empirical formula is \( \text{CH}_2 \).

Step1: Balance Oxygen atoms

On the left, \( \text{O}_2 \) has 2 O atoms. On the right, \( \text{H}_2\text{O} \) has 1 O atom. So, put coefficient 2 in front of \( \text{H}_2\text{O} \) to get 2 O atoms. Now the equation is: \( \text{H}_2 + \text{O}_2
ightarrow 2\text{H}_2\text{O} \).

Step2: Balance Hydrogen atoms

On the right, \( 2\text{H}_2\text{O} \) has 4 H atoms. On the left, \( \text{H}_2 \) has 2 H atoms. So put coefficient 2 in front of \( \text{H}_2 \). The balanced equation is: \( 2\text{H}_2 + \text{O}_2
ightarrow 2\text{H}_2\text{O} \). The coefficients are 2, 1, 2.

Answer:

C. 2, 3, 2

Question (Empirical Formula for \( \text{C}_2\text{H}_4 \))