Question

name
unit 8 mixed practice
complete each step for all of the following questions. we are now combining everything we have learned in this unit.
step 1: translate the sentence into a chemical equation.
step 2: balance the chemical equation by adding coefficients as needed.
step 3: identify the type of chemical reaction by writing the appropriate abbreviation in the space provided
s - synthesis d - decomposition c - combustion sr - single replacement dr - double replacement

1. dicarbon hexahydride reacts with oxygen gas to produce carbon dioxide and water
2. silver oxide decomposes upon heating to produce solid silver metal and oxygen gas.
3. calcium chloride reacts with fluorine gas to produce calcium fluoride and chlorine gas.
4. iron and oxygen gas reaction to produce iron (iii) oxide.
5. sodium phosphate reacts with calcium chloride to form calcium phosphate and sodium chloride.

Answer:

Question 1: Dicarbon hexahydride reacts with oxygen gas to produce carbon dioxide and water

Step 1: Translate to chemical equation

Dicarbon hexahydride is \( C_2H_6 \), oxygen gas is \( O_2 \), carbon dioxide is \( CO_2 \), water is \( H_2O \). So the unbalanced equation is:
\( C_2H_6 + O_2
ightarrow CO_2 + H_2O \)

Step 2: Balance the equation

• Carbon atoms: Left has 2, right has 1. So put 2 in front of \( CO_2 \):

\( C_2H_6 + O_2
ightarrow 2CO_2 + H_2O \)

• Hydrogen atoms: Left has 6, right has 2. So put 3 in front of \( H_2O \):

\( C_2H_6 + O_2
ightarrow 2CO_2 + 3H_2O \)

• Oxygen atoms: Right has \( 2 \times 2 + 3 \times 1 = 7 \), left has 2. To balance, use \( \frac{7}{2} \) for \( O_2 \), then multiply all coefficients by 2 to eliminate fractions:

\( 2C_2H_6 + 7O_2
ightarrow 4CO_2 + 6H_2O \)

Step 3: Identify reaction type

This is a combustion reaction (G), as a hydrocarbon reacts with oxygen to produce \( CO_2 \) and \( H_2O \).

Question 2: Silver oxide decomposes upon heating to produce solid silver metal and oxygen gas

Step 1: Translate to chemical equation

Silver oxide is \( Ag_2O \), silver is \( Ag \), oxygen gas is \( O_2 \). Unbalanced:
\( Ag_2O
ightarrow Ag + O_2 \)

Step 2: Balance the equation

• Oxygen atoms: Left has 1, right has 2. Put 2 in front of \( Ag_2O \):

\( 2Ag_2O
ightarrow Ag + O_2 \)

• Silver atoms: Left has \( 2 \times 2 = 4 \), right has 1. Put 4 in front of \( Ag \):

\( 2Ag_2O
ightarrow 4Ag + O_2 \)

Step 3: Identify reaction type

This is a decomposition reaction (D), as a single compound breaks down into simpler substances.

Question 3: Calcium chloride reacts with fluorine gas to produce calcium fluoride and chlorine gas

Step 1: Translate to chemical equation

Calcium chloride is \( CaCl_2 \), fluorine gas is \( F_2 \), calcium fluoride is \( CaF_2 \), chlorine gas is \( Cl_2 \). Unbalanced:
\( CaCl_2 + F_2
ightarrow CaF_2 + Cl_2 \)

Step 2: Balance the equation

• Calcium: 1 on left, 1 on right (balanced).
• Chlorine: 2 on left, 2 on right (balanced).
• Fluorine: 2 on left, 2 on right (balanced).

The equation is already balanced: \( CaCl_2 + F_2
ightarrow CaF_2 + Cl_2 \)

Step 3: Identify reaction type

This is a single replacement (SR) reaction, as fluorine (a more reactive halogen) replaces chlorine in \( CaCl_2 \).

Question 4: Iron and oxygen gas react to produce iron (III) oxide

Step 1: Translate to chemical equation

Iron is \( Fe \), oxygen gas is \( O_2 \), iron (III) oxide is \( Fe_2O_3 \). Unbalanced:
\( Fe + O_2
ightarrow Fe_2O_3 \)

Step 2: Balance the equation

• Iron atoms: Left has 1, right has 2. Put 2 in front of \( Fe \):

\( 2Fe + O_2
ightarrow Fe_2O_3 \)

• Oxygen atoms: Left has 2, right has 3. Use least common multiple (6). Put 3 in front of \( O_2 \) and 2 in front of \( Fe_2O_3 \):

\( 4Fe + 3O_2
ightarrow 2Fe_2O_3 \)

Step 3: Identify reaction type

This is a synthesis (S) reaction, as two substances combine to form a single compound.

Question 5: Sodium phosphate reacts with calcium chloride to form calcium phosphate and sodium chloride

Step 1: Translate to chemical equation

Sodium phosphate: \( Na_3PO_4 \), calcium chloride: \( CaCl_2 \), calcium phosphate: \( Ca_3(PO_4)_2 \), sodium chloride: \( NaCl \). Unbalanced:
\( Na_3PO_4 + CaCl_2
ightarrow Ca_3(PO_4)_2 + NaCl \)

Step 2: Balance the equation

• Phosphate (\( PO_4^{3-} \)): Left has 1, right has 2. Put 2 in front of \( Na_3PO_4 \):

\( 2Na_3PO_4 + CaCl_2
ightarrow Ca_3(PO_4)_2 + NaCl \)

• Calcium (\( Ca^{2+} \)): Left has 1, right has 3. Put 3 in front of \( CaCl_2 \):

\( 2Na_3PO_4 + 3CaCl_2
ightarrow Ca_3(PO_4)_2 + NaCl \)

• Sodium (\( Na^+ \)): Left has \( 2 \times 3 = 6 \), right has 1. Put 6 in front of \( NaCl \):

\( 2Na_3PO_4 + 3CaCl_2
ightarrow Ca_3(PO_4)_2 + 6NaCl \)

Step 3: Identify reaction type

This is a double replacement (DR) reaction, as ions ( \( Na^+ \) with \( Cl^- \), \( Ca^{2+} \) with \( PO_4^{3-} \)) exchange between compounds.

Final Answers (Reaction Types):

1. G (Combustion)
2. D (Decomposition)
3. SR (Single Replacement)
4. S (Synthesis)
5. DR (Double Replacement)

(For balanced equations, refer to each question’s Step 2.)