Chemical Reactions Lab

by Rachel, Chris P., Alex, and Kyra

Introduction

Primary Objective: To write balanced chemical equations
Reactants: The substances on the left side of the equation that are changed in the reaction
Products: The resulting substances on the right side of a chemical equation
Coefficients: A number that tells how many of each element/polyatomic ion/compound there are in an equation to keep it balanced

Secondary Objective: Observing evidence of chemical reactions
  • Formation of a precipitate
  • Formation of a gas
  • Change in temperature/emitting light
  • Change in color

Analysis of Reactions

Experiment 1: Copper (II) sulfate pentahydrate crystals decompose to form copper (II) sulfate and water
A) Evidence of chemical reaction:


  • color changed from blue to white
  • condensation formed on the sides of the test tube


B) Hydrate: to add water
C) This reaction is decomposition


Experiment 2: Potassium iodide reacts with lead (II) nitrate to yield potassium nitrate and lead iodide


A) Evidence of a chemical reaction:


  • color change from clear to yellow
  • powdery bits formed and it got thicker
B) "Reacts with" means that you combine the two or more elements/compounds together


C) This was a double replacement reaction

D) 2 KI + Pb(NO3)2 yields 2KNO3 + PbI2


Experiment 3: Magnesium reacts with oxygen gas to form Magnesium oxide

A) Evidence of a chemical reaction:


  • emits a bright white light
  • color change from silver to white
B) Since oxygen is in BrINClHOF, it means that it must have a subscript of 2 when it stands alone (not in a compound)


C) This is a synthesis chemical reaction

D) 2Mg + O2 yields 2MgO


Experiment 4: Zinc metal reacts with hydrochloric acid to produce Zinc chloride and hydrogen

A) Evidence of a chemical reaction:


  • loud squeaking sound and a quick burst of light
  • gas formation-condensation on the test tube
B) Cations are positively charged elements is a compound that go first when writing a compound in a balanced equation. Anions are negatively charged elements that are written after cations in compounds.


C) This is a single replacement chemical reaction

D) 2 Zn + 2HCl yields 2ZnCl +H2

E) The product found in the upside down test tube was hydrogen gas


Experiment 5: Hydrogen peroxide breaks down to form water and oxygen gas

A) Evidence of a chemical reaction:


  • condensation
  • emitted faint glowing orange light
B) A catalyst is a substance that speeds up a reaction without being changed itself in the process


C) This is a decomposition chemical reaction

D) MnO2

4HO2 yields 2H2O + 3O2

E) Oxygen would make the glowing splint reignite because oxygen is a reactant in combustion which makes fire

Experiment pictures

Conclusions

A)

  • i. dissolving salt in water is a chemical change
  • ii. melting ice is a physical change
  • iii. milk turning sour is a chemical change
  • iv. burning fireworks are a chemical change
  • v. a 2-liter bottle going flat is a chemical change
  • vi. frying an egg is physical change
B)
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