Chemical reactions

The goal of the lab was to show learn about chemical reactions. It showed the different types of chemical reactions (synthesis, decomposition, single replacement, double replacement, and combustion.) In the lab different elements and compounds were combined to observe chemical reactions and see what they could look like. The reactions also showed whether or not predictions that were made were accurate or not. The reactions were observed to see what would happen before, during, and after the eight chemical reaction and to see what the chemical reactions could produce.

Introduction

There are five types of chemical reactions: combustion, synthesis, decomposition, single replacement, and double replacement. To write an equation first it must be determined what type of reaction it is in order to predict the products accurately. Synthesis is the combination of two or three reactants into one single product. Decomposition is when one compound decomposes into two or more products. Single replacement is when there is a compound and an element and the element and a part of the compound are switched to for two different products. Double replacement is when there are two compounds and then the anions are switched to form two different compounds. Combustion is normally the reaction of a compound made up of hydrogen and carbon that reacts with oxygen to form water and carbon dioxide.

To begin to write the equation in ionic compounds the ions of each need to have a balanced charge. For example oxygen has a charge of -2 and sodium has a charge of +1 to make the charges equal the sodium must have a subscript of two to balance out the ions to equal zero. In reactions there is also the law of the conservation of mass. This law means that in chemical reactions there is the same amount of mass in the product as in the reactants whether it is in the form of a liquid, solid, or gas. To follow this law it is important to balance the equation. To do so coefficients have to be added on either side of the equation to make sure that there is an equal number of atoms of each element on either side of the equation. If it is an equation involving heat then there is a delta above the arrow to indicate that heat was added to create the reaction.

It is important to follow the safety rules in order to not get hurt or injured. It is important to wear goggles during the lab so that any liquids, gases, glasses, or extra materials doesn’t damage any eyes. It is also important to use hot mitts (whenever possible) to protect hands from potentially dangerous hot substances in order to prevent any burns and chemicals from landing on skin. It is also important to wear aprons whenever possible to prevent any damage to clothing or body from potentially dangerous chemicals, glass, or heat.

Hypotheses

Reaction A

2Mg(s) + O2(g) -> 2MgO(s)

Reaction B

CaO(s) +H2O(l) -> Ca(OH)2(aq)

Reaction C

3CuSO4(aq) +2Na3PO4(aq)-> Cu3(PO4)2(aq) +3Na2SO4(s)

Reaction D

NaHCO3(s) -> Na(s) + H2O(l) + CO2(g)

Reaction E

2NaBr(aq) + Cl2(aq) -> 2NaCl(aq) +Br2(l)

Reaction F

Zn(s) + 2HCl(aq) -> ZnCl2(aq) +H2(g)

Reaction G

NaHCO3(aq) + HC2H3O2(aq) -> NaC2H3O2(aq) +H2O(l) +CO2(g)

Reaction H

CuSO4(aq) +Zn(s) -> ZnSO4(s) + Cu(aq)

Observations

Reaction A

Before: Silver, rectangular shape, malleable

During: white, bright, light

After: white, powdery, broken up/ashy

Reaction B

Before: White powder and water

During: Power dissolving into water

After: Milky white, non-transparent, dark blue ph strip of 11, slightly thick

Reaction C

Before: copper sulfate: light green/blue, translucent; sodium phosphate: transparent

During: Two combined together, colors changing

After: Blue, opaque, swirls of color (not one shade), more liquid on top and some crystallization on the bottom

Reaction D

Before: White, powdery

During: Gas released and water conducted; blazing splint went out; cobalt II chloride paper turned pink

After: stayed powdery

Reaction E

Before: Both clear, transparent liquids

During: turned an orange/yellow color

After: stayed a dark orange, translucent

Reaction F

Before: Clear liquid, silver, non-constant pieces of zinc

During: Loud pop and flame goes up in test tube when splint is ignited, white, hot, some small bubbles

After: Milky white and zinc at bottom

Reaction G

Before: White and powdery

During: Bubbles a lot and dissolves a little

After: Baking soda dissolves a little and the precipitate has the baking soda at the bottom and a white liquid at the top

Reaction H

Before: Cu: blue, transparent: zinc: shiny, silver, malleable, rectangular

During: no difference at first, zinc starting to turn black

After: solution stayed somewhat the same but the zinc turned black

Conclusion

Reaction A: Synthesis

The magnesium strip reacting with the oxygen around it was what caused the bright, white light. At the end the magnesium strip was powdery and crumbly because it wasn’t just the magnesium anymore but magnesium oxide because the two combined because of the high amount of heat created by the flame. The reaction was a chemical reaction because there was a release in energy in both heat and light which was observed by the bright, white ball of light during the reaction. The reaction also had a change in color (the magnesium turned from silver to white) and the change wasn’t easily reversed because it would be very hard to turn the white ash back into magnesium and oxygen. The hypothesis was correct because both the magnesium and oxygen combined to form into a solid magnesium oxide.

2Mg(s) +O2(g)-> 2MgO(s)

Reaction B: Synthesis

The white powder dissolved into the water which was the combination of calcium oxide and water which formed the calcium hydroxide. The ph strip was a dark blue and was around a level of 11. The number eleven for the ph strip means that the solution created was basic. This means that there must be OH in the products rather than a H which would have meant that the product was acidic. Therefore the calcium oxide and water must have combined to form calcium hydroxide which contains OH in it. It also would be difficult to reverse the reaction because the calcium oxide and hydrogen were chemically combined so they would have to be uncombined by chemical means rather than just evaporating the water or by some other physical means. The hypothesis was correct because it believed that the calcium oxide and water would form calcium hydroxide and it was correct.

CaO(s) +H2O(l) ->Ca(OH)2(aq)

Reaction C: Double Replacement

The two solutions that were combined together formed two different products; a blue opaque liquid and a crystallized precipitate at the bottom. The precipitate formed at the bottom of the liquid was the copper II phosphate and the blue opaque liquid was sodium sulfate because phosphate and copper can form an aqueous compound according to the solubility chart while sulfate and sodium cannot. The reaction was a double replacement which meant that the phosphate and sulfate switched which elements they were combined with when the two were mixed together. The reaction was a chemical reaction because there was the formation of a precipitate and the change wasn’t easily reversed because it would be hard to turn a solid and an aqueous solution into two aqueous solutions. There was also a change in color from green and clear to a blue color which indicates a chemical reaction. The hypothesis was correct because the prediction was that copper II sulfate and sodium sulfate would produce copper II phosphate and sodium sulfate.

3CuSO4(aq) +2Na3PO4(aq)-> Cu3(PO4)2(aq) +3Na2SO4(s)

Reaction D: Decomposition

The blazing splint went out which indicates the presence of carbon dioxide as a gas. The cobalt II chloride paper turned pink which indicate that there was also water present. The gas released indicated the release of carbon dioxide as well and the liquid that condensed on the test tube indicated the release of water. This meant that when the sodium bicarbonate was heated the H,C, and O molecules were released and formed water and carbon dioxide. The remaining powder was the sodium left minus the hydrogen, carbon, and oxygen that were used for water and carbon dioxide. The reaction was a chemical reaction because there was the formation of carbon dioxide (a gas) and the release of water. The change also wasn’t easily reversible because it would be nearly impossible to make the water, carbon dioxide, and sodium turn back into one single compound. The hypothesis was correct because there was the decomposition of sodium bicarbonate into sodium, water, and carbon dioxide as was predicted.

NaHCO3(s)-> Na(s) +H2O(l)+CO2(g)

Reaction E: Single Replacement

The change in color from clear to yellow/orange was because there was the formation of the diatomic molecule of bromine. The two liquids of sodium bromide and chlorine formed the diatomic molecule of bromine. The products of sodium bromide and chlorine combined to produce sodium chloride and bromine in a single replacement reaction. The reaction was a chemical reaction because there was a change in color from clear to yellow/orange which indicates a chemical reaction. It was also a change that wasn’t easily reversed because the sodium and chlorine were chemically combined together rather than just physically which shows that it is a chemical reaction as well. There was also the creation of the diatomic molecule, bromine because it is a diatomic element because it only comes in two molecules when it is by itself. The hypothesis was correct because it was believed that it was a single replacement reaction in which the sodium bromide and chlorine were chemically reacted to form sodium chloride and bromine.

2NaBr(aq) + Cl2(aq) -> 2NaCl(aq) +Br2(l)

Reaction F: Single Replacement

The change in color occurred because of the reaction of zinc and hydrochloric acid which released hydrogen and left zinc and chloride. The loud pop from the blazing splint also indicated the release of hydrogen gas rather than carbon dioxide. The zinc caused the hydrogen to be released from hydrochloric reaction but left behind the chlorine which should have combined with the zinc to form zinc chloride. However, there was an excess of zinc used which meant that there was still some zinc leftover but this was simply an error in the lab. The reaction was a chemical reaction because the change also wasn’t easily reversible and there was a change in color from silver to white. There was a formation of hydrogen gas which indicates a chemical reaction as well and would make it even harder to reverse the chemical reaction. The hypothesis was correct because it was believed to be a single replacement reaction which produced zinc chloride and hydrogen gas and the hypothesis was correct. The reaction when the wooden splint ignited the hydrogen was H2 +O2 -> H2O which was a combustion reaction.

2Zn(s) + 2HCl(aq) -> 2ZnCl(aq) +H2(g)

Reaction G: Double Replacement/Decomposition

The sodium hydrogen carbonate and vinegar combined to form a precipitate, gas, and solution within the reaction. The bubbles produced by this reaction was the release of carbon dioxide because there was both carbon and oxygen in the sodium hydrogen carbonate and vinegar. The carbon dioxide was the gas that was produced. The precipitate formed was sodium acetate because the sodium of the sodium hydrogen carbonate and the acetate of the vinegar combined together. The liquid was water because the hydrogen, water, and oxygen broke down into both carbon dioxide and water. It was a chemical reaction because there was the formation of carbon dioxide which is an indicator of a chemical reaction as well as the formation of a precipitate. However, the change wasn’t easily removed because it would be nearly impossible to create two liquids from gas, one liquid, and precipitate. The hypothesis was correct because it was believed that vinegar and sodium hydrogen carbonate would form sodium acetate, water , and carbon dioxide which was the correct theory.

NaHCO3(aq) + HC2H3O2(aq) -> NaC2H3O2(s) +H2O(l) +CO2(g)

Reaction H: Single replacement

In the reaction the zinc turned black while the solution remained somewhat the same. The zinc turned black because it was gaining the sulfate (sulfur and oxygen.) Meanwhile the copper solution lost the sulfate that the zinc gained. It was a chemical reaction because there was a change in color of the zinc from silver to black which is an indicator of a chemical reaction. The change also wasn’t easily reversed because both the zinc and the solution were chemically changed and it would be hard to have the copper gain the sulfate back from the zinc. The hypothesis was correct because it was believed that it would be a single replacement reaction and it was correct because the copper sulfate and zinc turned into zinc sulfate and copper.

CuSO4(aq) +Zn(s) -> ZnSO4(s) +Cu9(aq)

The lab showed that chemical reactions can be very unpredictable. Even though a hypothesis might be based on perfectly logical claims, science doesn’t always follow these ideas. It also showed that chemical reactions can create products that are very different from the reactants. It was interesting to see that two liquids can form to combine a solid or a gas. The lab demonstrated the law of conservation of mass as well because it showed that no matter how the states were changed there was still the same mass before and after the reaction.

Source: Essay UK - https://www.essay.uk.com/essays/science/chemical-reactions/


Not what you're looking for?

Search our thousands of essays:

Search:


About this resource

This Science essay was submitted to us by a student in order to help you with your studies.


  • Order a custom essay
  • Print this page
  • Search again

Word count:

This page has approximately words.


Share:


Cite:

If you use part of this page in your own work, you need to provide a citation, as follows:

Essay UK, Chemical reactions. Available from: <https://www.essay.uk.com/essays/science/chemical-reactions/> [21-05-19].


More information:

If you are the original author of this content and no longer wish to have it published on our website then please click on the link below to request removal:


Latest essays in this category:


Our free essays:

badges