Question

balancing equations - phet simulator
instructions: open the balancing chemical equations simulation on the phet website or app. open the “introduction” screen, choose the “my recipe” tab (top - right corner) in “tools”.
at the bottom of the page, choose the make ammonia option.

1. in the equation, is n₂ considered a reactant or a product?
2. in the equation, is nh₃ considered a reactant or a product?
3. balance the equation using the simulator. write the balanced coefficients below.

__n₂ + h₂ → __nh₃

1. in the boxes below, draw the particles representing the balanced equation.

(there are two boxes with an arrow between them)

1. a bar graph is displayed above the particle diagram. what do these bars tell us? (choose the bar graph in the “tools” menu if you havent already)
2. in the “tools” menu, choose the scale icon. what does that scale tell us?
3. the law of conservation of mass states that the mass of the ____ (reactants or products) is equal to the mass of the ____ (reactants or products).

Explanation:

Step1: Balance nitrogen atoms

Count N atoms: Reactant side has 2 (from $\text{N}_2$), product side has 1 (from $\text{NH}_3$). Add coefficient 2 to $\text{NH}_3$:
$\text{N}_2 + \text{H}_2
ightarrow 2\text{NH}_3$

Step2: Balance hydrogen atoms

Now H atoms: Product side has 6 (2×3 from $2\text{NH}_3$), reactant side has 2 (from $\text{H}_2$). Add coefficient 3 to $\text{H}_2$:
$\text{N}_2 + 3\text{H}_2
ightarrow 2\text{NH}_3$

Step3: Verify balanced equation

Check atom counts: N=2 on both sides, H=6 on both sides.

Answer:

1. For reactant/product identification:

• $\text{N}_2$: Reactant
• $\text{H}_2$: Reactant
• $\text{NH}_3$: Product

1. Balanced coefficients: $\boldsymbol{1}$ $\text{N}_2 + \boldsymbol{3}$ $\text{H}_2

ightarrow \boldsymbol{2}$ $\text{NH}_3$

1. Particle diagram:

• Left box (reactants): 1 molecule of $\text{N}_2$ (two bonded spheres) + 3 molecules of $\text{H}_2$ (two bonded spheres each)
• Right box (products): 2 molecules of $\text{NH}_3$ (one central sphere bonded to three smaller spheres)

1. Bar graph meaning: The bar graph shows the relative number of moles (or particle counts) of each reactant and product, confirming the ratio from the balanced equation.
2. Scale meaning: The scale shows that the total mass of the reactants equals the total mass of the products.
3. Law of Conservation of Mass: The mass of the reactants is equal to the mass of the products