Stoichiometry Reaction Lab

Why it matters

Imagine baking a cake with exactly enough flour for 100 cookies, but only enough sugar for 50. The sugar runs out first, dictating the final count.

The idea in plain words

Balance check: Verify that the number of Na, O, H, and Cl atoms is identical on both sides of the arrow.

Predict first

If you mix 1 mole of NaOH with 1 mole of HCl, how many moles of NaCl form?

The balanced equation NaOH + HCl → NaCl + H₂O shows a 1:1:1:1 ratio. One mole of each reactant yields exactly one mole of salt.

• 0.5 moles
• 1 mole — correct
• 2 moles
• It depends on the temperature

What you do

Add the NaOH to the dilute acid drop by drop. Phenolphthalein stays colourless in the acid and turns faint pink at the end point, when the moles exactly balance.

Check yourself

In the reaction 2Na + 2H₂O → 2NaOH + H₂, if 2 moles of Sodium react, how many moles of Hydrogen gas are produced?

The coefficient of H₂ is 1, while Na is 2. The ratio is 2:1, so 2 moles of Na yield 1 mole of H₂.

Why does the beaker feel warm during the NaOH + HCl reaction?

Neutralisation reactions release energy as heat, making the container feel warm.

In C + O₂ → CO₂, if you have excess Oxygen, what limits the amount of CO₂ produced?

The limiting reagent is the one that runs out first. Since Oxygen is in excess, Carbon determines the maximum product yield.

• 1 mole — correct
• 2 moles
• 4 moles
• The reaction is exothermic — correct
• The reaction is endothermic
• Friction from stirring
• The amount of Carbon — correct
• The amount of Oxygen
• The temperature of the flame