Chemical Reactions Lab Report

Rachel Everage, Isabella Trevino, Gavin Craig, Mason Warren

Introduction

Objectives

Our primary objective in this lab was to write the balanced chemical equations for the

reactions that we saw. To write these balanced equations we had to know what reactants, products, and coefficients are. In a chemical equation, reactants are on the left side of the arrow and are what takes part in a reaction and undergoes a change during it. The products are on the right side of the arrow in an equation and are the result of the reaction.
The secondary objective in this lab was to find the main pieces of evidence that prove the reactions were chemical and not just a physical change. The four observations that could be used as evidence that a chemical reaction occurred are: the formation of a precipitate (a solid), the formation of a gas, a change in temperature/ emission of light, and a change in color.

Analysis of Reactions

Experiment One

Copper (II) sulfate pentahydrate crystals decompose to form copper (II) sulfate and water.

  • In this experiment we witnessed several indicators of a chemical reaction. The blue gritty powder turned into a white powder and water formed on the sides of the test tube when heated with the butane torch. A gas was also formed during this reaction.
  • The term hydrate is defined as a solid compound that contains a definite percentage of bound water.
  • Since there is only one reactant in the compound that makes it a decomposition style reaction.
Chem Lab | Experiment One

Experiment Two

Potassium Iodide reacts with Lead (II) Nitrate to yield…

  • The substance immediately turned into a bright shade of yellow. While we were waiting for a reaction to occur, it slowly became a solid. These were both indicators that a chemical reaction had taken place.
  • The words “reacts with” in a balanced equation mean that two or more substances are combining/ mixing to make a new substance.
  • This reaction is a double replacement reaction because there are two compounds on the reaction side of the equation.
  • Balanced equation: 2KI + Pb(NO3)2---> 2KNO3 + PbI2

Bolded numbers are subscripts.

Chem Reactions | Experiment Two

Experiment Three

Magnesium reacts with oxygen gas to form…

  • The evidence we saw that indicated a chemical reaction was a bright light emission and a color change. The silver piece of magnesium turned into a white powder after being heated with a butane torch. It also produced a very bright, white light as seen in the video below.
  • Oxygen is one of the elements in “BRINClHOF”. This tells us that whenever oxygen is by itself in an equation (meaning it is not apart of a compound) it will always have a subscript of 2.
  • This is a synthesis reaction because a single element and another single element react together to form one compound.
  • Balanced equation: 2Mg + O2 ---> 2MgO

Bolded numbers are subscripts.

Chem Lab | Experiment Three

Experiment Four

Zinc metal reacts with hydrochloric acid to produce...

  • The evidence we saw that proved this experiment was a chemical reaction included the formation of a light yellow colored gas, and a change in temperature. When we added the zinc to the hydrochloric acid it immediately began to heat up.
  • In hydrochloric acid, hydrogen in the cation and chlorine is the anion. The term cation refers to the positively charged ion in a compound while an anion is a negatively charged ion in a compound.
  • This is a single replacement reaction because there is a single element and a compound on the reaction side of the equation.
  • Balanced equation: Zn+ 2HCl ---> ZnCl2 + H2

Bolded numbers are subscripts.

  • The identity of the gas we collected in this experiment is Zinc Chloride gas.

Experiment Five

Hydrogen peroxide breaks down to form water and oxygen gas.

  • One piece of evidence we observed that proves this was a chemical reaction was a color change. The substance immediately turned black once manganese dioxide was added. A gas was also formed during this reaction.

  • The manganese dioxide we used in this experiment is considered a catalyst. A catalyst is defined as a substance that speeds up a chemical reaction without undergoing a permanent chemical change itself during the reaction.

  • This is a decomposition reaction because there is only one reactant (a compound) that breaks down into two elements.

  • _____________________________________________MnO2__________________

    Balanced equation including catalyst: 2H2O2 ----> 2H2O +O2

Bolded numbers are subscripts.

  • During this experiment when we put the glowing wooden splint in the test tube it reignited. This happened because of the oxygen gas produced during the reaction.

Chem Lab | Experiment 5

Conclusion

Physical or chemical change?

i. Dissolving salt in water: Physical

ii. Melting ice: Physical

iii. Milk turning sour: Chemical

iv. Burning fireworks: Chemical

v. A 2-liter bottle going flat: Chemical

vi. Frying an egg: Chemical

The chart is below.
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