Question

review:

1. look at the following 2 equations. label and highlight the reactants in one color and the products in another color.

a. na + cl → nacl
b. ca + 2h₂o → ca(oh)₂ + h₂

1. what is a subscript and what specifically a subscript tell you? provide an example and label.

Explanation:

Question 1: Label Reactants and Products in Chemical Equations

Part (a): $\boldsymbol{\ce{Na + Cl -> NaCl}}$

• Reactants: Substances on the left of the arrow ($

ightarrow$). These are the starting materials that undergo reaction.

• $\ce{Na}$ (Sodium) and $\ce{Cl}$ (Chlorine, likely $\ce{Cl2}$ in reality, but as written)
• Products: Substance on the right of the arrow. This is the result of the reaction.
• $\ce{NaCl}$ (Sodium Chloride)

Part (b): $\boldsymbol{\ce{Ca + 2H2O -> Ca(OH)2 + H2}}$

• Reactants: Substances on the left of the arrow.
• $\ce{Ca}$ (Calcium) and $\ce{2H2O}$ (Water, with a coefficient of 2)
• Products: Substances on the right of the arrow.
• $\ce{Ca(OH)2}$ (Calcium Hydroxide) and $\ce{H2}$ (Hydrogen Gas)

Question 2: What is a Subscript?

Definition:

A subscript is a small number written below and to the right of an element’s symbol in a chemical formula. It tells you the number of atoms of that element in one molecule (or formula unit) of the compound.

Example:

Consider the formula for water: $\boldsymbol{\ce{H2O}}$.

• The subscript “2” after $\ce{H}$ means there are 2 hydrogen atoms in one molecule of water.
• The subscript “1” (implied, not written) after $\ce{O}$ means there is 1 oxygen atom in one molecule of water.

Labeled Example:

In $\ce{H2O}$:

• Element: $\ce{H}$ (Hydrogen), Subscript: $2$ → “2 H atoms per $\ce{H2O}$ molecule.”
• Element: $\ce{O}$ (Oxygen), Subscript: $1$ (implied) → “1 O atom per $\ce{H2O}$ molecule.”

Final Answers (Summarized):

1. Equation (a):

• Reactants: $\ce{Na}$, $\ce{Cl}$
• Product: $\ce{NaCl}$

Equation (b):

• Reactants: $\ce{Ca}$, $\ce{2H2O}$
• Products: $\ce{Ca(OH)2}$, $\ce{H2}$

1. Subscript: A small number in a chemical formula (e.g., “2” in $\ce{H2O}$) that shows the number of atoms of the preceding element in one molecule. Example: $\ce{H2O}$ has 2 H atoms and 1 O atom per molecule.

Answer:

Question 1: Label Reactants and Products in Chemical Equations

Part (a): $\boldsymbol{\ce{Na + Cl -> NaCl}}$

• Reactants: Substances on the left of the arrow ($

ightarrow$). These are the starting materials that undergo reaction.

• $\ce{Na}$ (Sodium) and $\ce{Cl}$ (Chlorine, likely $\ce{Cl2}$ in reality, but as written)
• Products: Substance on the right of the arrow. This is the result of the reaction.
• $\ce{NaCl}$ (Sodium Chloride)

Part (b): $\boldsymbol{\ce{Ca + 2H2O -> Ca(OH)2 + H2}}$

• Reactants: Substances on the left of the arrow.
• $\ce{Ca}$ (Calcium) and $\ce{2H2O}$ (Water, with a coefficient of 2)
• Products: Substances on the right of the arrow.
• $\ce{Ca(OH)2}$ (Calcium Hydroxide) and $\ce{H2}$ (Hydrogen Gas)

Question 2: What is a Subscript?

Definition:

A subscript is a small number written below and to the right of an element’s symbol in a chemical formula. It tells you the number of atoms of that element in one molecule (or formula unit) of the compound.

Example:

Consider the formula for water: $\boldsymbol{\ce{H2O}}$.

• The subscript “2” after $\ce{H}$ means there are 2 hydrogen atoms in one molecule of water.
• The subscript “1” (implied, not written) after $\ce{O}$ means there is 1 oxygen atom in one molecule of water.

Labeled Example:

In $\ce{H2O}$:

• Element: $\ce{H}$ (Hydrogen), Subscript: $2$ → “2 H atoms per $\ce{H2O}$ molecule.”
• Element: $\ce{O}$ (Oxygen), Subscript: $1$ (implied) → “1 O atom per $\ce{H2O}$ molecule.”

Final Answers (Summarized):

1. Equation (a):

• Reactants: $\ce{Na}$, $\ce{Cl}$
• Product: $\ce{NaCl}$

Equation (b):

• Reactants: $\ce{Ca}$, $\ce{2H2O}$
• Products: $\ce{Ca(OH)2}$, $\ce{H2}$

1. Subscript: A small number in a chemical formula (e.g., “2” in $\ce{H2O}$) that shows the number of atoms of the preceding element in one molecule. Example: $\ce{H2O}$ has 2 H atoms and 1 O atom per molecule.