factors affecting reaction rates terms

part 1: effect of metal activity

purpose?

to see how the type of metal affects reaction rate when reacting with the same acid.

what stayed consistent for part 1?

HCl, same concentrations

temperature and volume of acid

setup and timing method

what changed for part 1?

type of metal

• mg

• zn

• cu

Magnesium Reaction Performed - Part 1

Mg(s) + 2 HCl(aq) → MgCl₂(aq) + H₂(g)

Zinc Reaction Performed - Part 1

Zn(s) + 2 HCl(aq) → ZnCl₂(aq) + H₂(g)

Copper Reaction Performed - Part 1

Cu(s) + 2 HCl(aq) → No Reaction

Mg Reaction Observed - Pt 1

rapid bubbling, vigorous reaction

fastest 

Zn Reaction Observation - Pt 1

moderate bubbling

moderate

Cu Reaction Observed - Pt 1

no bubbling, no visible change

no reaction

conclusion of part 1

reactivity determines rate

mg > zn > cu because magnesium is more active than hydrogen, zinc is less reactive, and copper is below hydrogen in the activity series 

it cannot replace H+

part 2 - effect of acid strength

purpose 

to determine how the strength of the acid affects the rate of hydrogen gas formation with a constant metal

what stayed consistent in part 2?

metal: magnesium (same size and amount)

set up, timing method, and overall temperature conditions (as much as possible).

what changed in part 2?

type of acid:

• H₂SO₄

• HCl

• H₃PO₄

• CH₃COOH

each acid has a different ability yo ionize and release H+ ions

H₂SO₄ Reaction Performed - Pt 2

Mg + H₂SO₄ → MgSO₄ + H₂

Fastest Rate

Strong Acid Strength

HCl Reaction Performed - Pt 2

Mg + 2 HCl → MgCl₂ + H₂

Moderate Rate

Strong Acid Strength

H₃PO₄ Reaction Performed - Pt 2

3 Mg + 2 H₃PO₄ → Mg₃(PO₄)₂ + 3 H₂

Slow Rate

Weak Acid Strength

CH₃COOH Reaction Performed

Mg + 2 CH₃COOH → Mg(CH₃COO)₂ + H₂

Weak Rate

Weakest Acid Strength

conclusion of part 2

all acids reacted with magnesium only

reaction rate increased with acid strength - strong acids (H₂SO₄, HCl) ionize completely, realsing more H+ ions - more collisions with Mg - faster H2 gas formation. 

part 3 - effect of concentration

purpose?

to see how changing the concentration of reactants (HIO₃) affects reaction rate.

what stayed consistent for part 3?

• same temperature, same reactants (HIO₃, H₂SO₃, starch).

• total solution volume kept constant (2.0 mL).

• same color indicator method (appearance of blue color)

what changed for part 3?

concentration of HIO₃ solution

reactions performed during part 3

HIO₃(aq) + H₂SO₃(aq) → I₂(aq) + H₂SO₄(aq) + H₂O(l)
I₂ + starch → blue complex (signals reaction completion).

sample calculation for part 3

[HIO₃] = (0.010M) (VHIO₃​) / Vtotal​

for 11 drops (0.55 mL = 5.5 × 10⁻⁴ L):

Vtotal​ ≈ 1.25 × 10−3L ⇒ [HIO₃] = 0.0046M

conclusion for part 3

as concentration goes up, the rate also goes up.

more reactant particles per volume - higher collision frequency - faster color change (blue complex forms sooner).

part 4: effect of temperature

purpose?

to determine how temperature changes reaction rate for the same reactants

what stayed consistent for part 4

same chemicals and concentrations

same procedure and timing method

what changed for part 4

temperature of the solution

(cold, room temp, warm)

reaction used for part 4

same iodine clock reaction as part III:
HIO₃ + H₂SO₃ → I₂ + H₂SO₄ + H₂O
(I₂ + starch → blue color).

ice bath observations - pt 4 - 3 degrees celsius 

very slow color change

slow rate 

room temp observations - pt 4 - 31 degrees celsius

moderate time

medium rate 

warm observations - pt 4 - 68 degrees celsius

very quick blue color

fastest rate 

conclusion of part 4

higher temperature means higher average kinetic energy which leads to more frequent and energetic collisions.

more molecules exceed activation energy means faster rate 

part 5: effect of catalyst

purpose?

to test how adding a catalyst affects the rate of decomposition of hydrogen peroxide.

what stayed consistent in part 5?

amount and concentration of H₂O₂ solution.

same setup and timing method

what changed in part 5?

presence or absence of catalyst (MnO₂).

reaction performed in part 5

2 H₂O₂(aq) → 2 H₂O(l) + O₂(g)

catalyst in part 5

MnO₂ (manganese dioxide)

observations with MnO₂

immediate and rapid bubbling of O₂ gas.

solution turns black (MnO₂ solid particles).

observations without MnO₂

very slow gas release.

conclusion of part 5

catalyst lowers the activation energy (Ea) allowing the reaction to proceed faster.

MnO₂ is not consumed; it only provides an alternate reaction pathway.