Question

which of the following is the correctly balanced chemical equation for the reaction of ca(oh)₂ and hno₃?
○ ca(oh)₂ + hno₃ → ca²⁺ + no₃⁻
○ ca(oh)₂ + 2hno₃ → 3h₂o + 2no₃⁻
○ ca(oh)₂ + 3hno₃ → h₂o + cano₃
○ ca(oh)₂ + 2hno₃ → 2h₂o + ca(no₃)₂

Explanation:

1. Identify the reaction type: $\ce{Ca(OH)_{2}}$ (a base) reacts with $\ce{HNO_{3}}$ (an acid) in a neutralization reaction, producing a salt and water. The general form is $\text{Base} + \text{Acid}

ightarrow \text{Salt} + \text{Water}$.

1. Analyze reactants and products:

• Reactants: $\ce{Ca(OH)_{2}}$ (contains $\ce{Ca^{2+}}$, $\ce{OH^-}$) and $\ce{HNO_{3}}$ (contains $\ce{H^+}$, $\ce{NO_3^-}$).
• Products: The salt should be $\ce{Ca(NO_{3})_{2}}$ (from $\ce{Ca^{2+}}$ and $\ce{NO_3^-}$) and water ($\ce{H_{2}O}$ from $\ce{H^+}$ and $\ce{OH^-}$).

1. Balance the equation:

• For $\ce{Ca}$: 1 on left ($\ce{Ca(OH)_{2}}$) and 1 on right ($\ce{Ca(NO_{3})_{2}}$) – balanced.
• For $\ce{NO_3^-}$: 2 on right ($\ce{Ca(NO_{3})_{2}}$), so we need 2 $\ce{HNO_{3}}$ on left.
• For $\ce{OH^-}$: 2 on left ($\ce{Ca(OH)_{2}}$), so we need 2 $\ce{H_{2}O}$ on right (since each $\ce{H_{2}O}$ comes from 1 $\ce{H^+}$ and 1 $\ce{OH^-}$; 2 $\ce{OH^-}$ react with 2 $\ce{H^+}$ to make 2 $\ce{H_{2}O}$).
• Checking all atoms:
• $\ce{Ca}$: 1 (left) = 1 (right).
• $\ce{O}$: In $\ce{Ca(OH)_{2}}$: 2, in $2\ce{HNO_{3}}$: $2\times3 = 6$; total left: $2 + 6 = 8$. In $2\ce{H_{2}O}$: $2\times1 = 2$, in $\ce{Ca(NO_{3})_{2}}$: $2\times3 = 6$; total right: $2 + 6 = 8$.
• $\ce{H}$: In $2\ce{HNO_{3}}$: $2\times1 = 2$, in $\ce{Ca(OH)_{2}}$: $2\times1 = 2$; total left: $2 + 2 = 4$. In $2\ce{H_{2}O}$: $2\times2 = 4$ – balanced.
• $\ce{N}$: In $2\ce{HNO_{3}}$: 2, in $\ce{Ca(NO_{3})_{2}}$: 2 – balanced.

Other options fail balancing:

• Option A: Missing the salt and water products (shows ions, not a balanced neutralization equation).
• Option B: Incorrect product (has $\ce{NO_3^-}$ instead of the salt $\ce{Ca(NO_{3})_{2}}$) and unbalanced $\ce{Ca}$.
• Option C: Incorrect product formula ($\ce{CaNO_{3}}$ should be $\ce{Ca(NO_{3})_{2}}$) and unbalanced atoms.

Answer:

D. $\ce{Ca(OH)_{2} + 2HNO_{3}
ightarrow 2H_{2}O + Ca(NO_{3})_{2}}$