Properties and Reactivity of Aqueous Solutions PDF

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Properties and Reactivity of Aqueous Solutions Introduction There are two classes of compounds based on the type of ions or elements, from which they are composed of. These two classes of compounds are soluble or miscible compounds. The soluble compounds are able to form ions in a solution and the way they behave is by dissociating in water to form cations and anions. On the other hand, miscible solutions are compounds that exist in liquid form. Ions are charged atoms that have the capacity of conducting electricity. Besides that, the ions can also conduct electrical currents. Molecules are neutral and can be a group of more than two atoms that are bonded together. The electrical conductivity of an aqueous solution is the flow of electrons in a conductive material. Now, electrical conductivity is considered a physical property of a substance because it is a characteristic that does not change the substance’s properties. Soluble substances are classified by the fraction of ions that conduct current this is based on the ability to conduct electricity. It is known that if the solute is completely dissolved in water and besides has a large fraction of ions it means that it can conduct a big current, furthermore, the solution then is a strong electrolyte. Now, for weak electrolyte is a little bit different, if the substance is a little bit soluble in water and therefore it will not conduct too much current. Moreover, if the solutions are not able to dissolve in the solution then it is non-electrolyte because it will not conduct any current. Electrical conductance is considered to be evidence for a chemical reaction because it has a movement and flow of electrons. This is true because the electrons that are being gained and the electrons that are being lost in the chemical reaction can be noticed in this specific experiment. The reason for performing this experiment was to

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be able to identify some types of aqueous compounds, observed the directions of these chemical compounds, compared the conductivity between them whether it was strong electrolyte, weak electrolyte, or non-electrolyte, use the electrical conductivity of substances and use the solubility rules to identify whether a chemical reaction occurred, to be able to predict the products being produced by these reactions, and to be able to write net ionic equations. Conductivity was tested in this experiment by using a conductivity apparatus to test different solutions. However, in order to conduct this experiment, there was a lot of safety procedural precautions that needed to be considered when conducting this experiment, for instance, all the chemicals were handled with care to prevent contamination between chemicals. Substances were carefully handled such as H2SO4, Ca(NO3)2, HCl, NH4OH, and other chemicals that are also corrosive and can serious eye damage or skin burns if they come in contact with your skin. These hazards were avoided by wearing proper PPE as well as washing our hands thoroughly after handling the reagents. II. Results AnalysisA. Data and Calculations Part I Evidence of Ions in Aqueous Solution

Solution Samples: Na2CO3 (aq)

Substance Form in Conductivity Testing Water (Ions, Molecules, or Both Apparatus Solid Observations

Electrolytic Properties of (SE-Strong electrolyte, Ionized or WE-weak electrolyte, or Non-ionized NE -nonelectrolyte Formula

HF (aq)

Red & Green Bulbs Ions Glow Molecules & few ions Red Bulb Glows or both

CaCl2 (s)

No Glow

Solid

NE

CaCl2 (s)

Red glow

Molecules and few ions

WE

H2O (l)

Top Water

SE

2 Na+ (aq) CO3-2 (aq)

WE

HF (l), H+ (aq), F(aq)

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Distilled water Red glow

Molecules

WE

H2O (l)

NaCl (s)

No Glow

Solid

NE

NaCl (s)

NaCl (aq)

Red and Green

Ions

SE

Na+ (aq) Cl-(aq)

CaCO3 (s)

No Glow

Solid

NE

Ca2+ (aq) CO32- (aq)

CaCO3 in water (l)

Red Glow

Both

WE

Ca2+ (aq) CO32- (aq) + H2O (l)

C12H22O11 (l)

Red Glow

Both

WE

C12H22O11 (l)

HCl (aq)

Red and green Glow Ions

SE

H+ (aq) Cl- (aq)

CH2H3O2 (aq) Red Glow

Ions

WE

H+ (aq) C2H302- (aq)

NH4OH (aq)

Ions

WE

NH4+(aq) OH-(aq)

Ca(NO3)2 (aq) Red and green Glow Ions

SE

Ca2+ (aq) 2NO3 (aq)

Red Glow

Table 1: Evidence of Ions in Aqueous Solution Part II Reactivity of Aqueous Solution: Typical Chemical Reactions and Net Ionic Equations A. Reaction between 0.1M HC2H3O2 and 0.1M NH4OH

Solution

Conductivity Testing Electronic Properties of Apparatus Observations Solutions (SE, WE, or (Bulbs Glow Observation) NE)

Ionized or Non-ionized Formula

HC2H3O2 (aq)

Red Glow

WE

H+ (aq) C2H3O2- (aq)

NH4OH (aq)

Red Glow

WE

NH4+ (aq) OH- (aq)

SE

H-(aq)+ C2H3O2+(aq) + NH4+ (aq) + OH-

HC2H3O2 + NH4OH

Red and Green Glow

Complete Balance Equation: HC2H3O2 (aq) + NH4OH (aq) →H2O (l) + NH4C2H3O2 (aq) Type of Chemical Reaction: Double displacement (Neutralization) reaction. Total Ionic Equation: H+ (aq) C2H3O2- (aq) + NH4+ (aq) OH- (aq) → H2O (l) + NH4C2H3O2 (aq) Net Ionic Equation: H+ (aq) + OH- (aq) → H2O (l) Table 2: Reaction between 0.1M HC2H3O2 and 0.1M NH4OH

B. Reaction Between H2CO2 and Saturated Ba(OH)2 Solutions

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Solutions

Conductivity Testing Electronic Properties of Apparatus Observations Solutions (SE, WE, or (Bulbs Glow Observation) NE)

Ionized or Non-ionized Formula

Di H2O (l)

Red dim

WE

H2O (l)

H2O (l) + CO2 (g) →

Red bright

WE

H2O (l) + CO2 (g)

Ba(OH)2 (aq)

Red and Green

SE

Ba2+ (aq) OH- (aq)

WE

Ba2+ (aq) 2OH- (aq) + CO2 (g)

Ba(OH)2 + CO2 (g)

Red

A. Complete Balance Equation when blowing CO2 in water (use the product to complete equation in B): H2O (l) + CO2 (g) → H2CO3(aq) Type of Chemical Reaction: Synthesis Reaction B. Complete Balance Equation between: Ba(OH)2(aq) + CO2(g) → BaCO3(s) + H2O(l) Type of Chemical Reaction: Acid-base Double displacement (Neutralization) reaction. Total Ionic Equation: Ba2+ (aq) + 2OH- (aq) + CO2(g) → BaCO3(s) + H2O(l) Net Ionic Equation Ba2+ (aq) + 2OH- (aq) + CO2(g) → BaCO3(s) + H2O(l) Table 3: Reaction Between H2CO2 and Saturated Ba(OH)2 Solutions Part III Conductivity of Household/ Commercial Products

Solutions

Conductivity Testing Electrolytic Ionized or Apparatus Properties of Solution Primary Compound Non-ionized or Solute Formula Formula Observations (Glow) (SE, WE, or NE) NG

Rubbing Alcohol Baking soda solution

NE Red and Green

SE

Molecular compound

C3H8O (aq)

Strong base

Na+(aq) HCO3- (aq)

Weak acid

H-(aq) C2H3O2+(aq)

Red and Greem Vinegar

WE

5% Dextrose intravenous (IV) solution Red

SE

Strong base

C6H12O6 - (aq) H2O (l)

Gatorade or any

SE

Strong acid

K+(aq) Na+(aq)

Red and Green

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Energy Drink

Mg2+ (aq) C6H12O6 (aq)

Table 4: Conductivity of Household/ Commercial Products In part II Bof the experiment it is important to point out that the complete ionic equation is similar to the complete ionic equation because in the reaction there were no expectators ions that could be removed because the reaction formed H2O (l) and BaCO3(s). In this particular case, all the ions in the reaction took part in the chemical reaction. In part III of the experiment, it is import to note that there are much more ions but the most important were collected.

B. Discussion Part I Conductivity Testing - Evidence for Ions in Aqueous Solution In this part of the experiment as well as the others, the conductivity test was performed by using conductivity apparatus to be able to test different solutions. The conductivity of the solution was based on the light that it will conduct, this was then classified as strong, weak, or non-electrolyte. If both of the lights (red and green glow), indicated a strong electrolyte if only the red light glow it indicated a week electrolyte and if there was no light it indicated that there was no conductivity. After each test, the electrode had to be rinsed and cleaned to avoid any misreading from the previous chemical that was read and to make sure the following reading was accurate. The conductivity readings of the distilled water show a very dim light which was slightly noticeable, the topwater on the other hand show a brighter light red light. The reason why they differed from one another is that the topwater have different minerals as well as more ions which made the light to be brighter. On the other hand, the distilled water undergoes the removal of ions and that is why topwater conducts more conductivity. The conductivity reading of solid NaCl indicated that there was no glow while the NaCl solution indicated a strong electrolyte which showed both, red and green glow. This indicated that NaCl plus water have a

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strong conductivity while NaCl solid state, the ions of the compound are not moving but when NaCl is dissolved in water, the compound dissociated into ions moving around. Now the conductivity reading of solid and solution of CaCO3 was somewhat similar to NaCl when the solution CaCO3 was in its solid-state there was no glow but when the solution of CaCO3 was in water it showed red light. This indicated that when the solution is dissolved, ions are released and move around, however, the red glow indicated a weak electrolyte. In this part of the experiment, aqueous NaCl, aqueous HCl, and aqueous Ca(NO3)2, were considered strong electrolytes because they completely dissociated in water and because these were the only electrolytes that showed both green and red glow. Now topwater, distilled water, aqueous CaCO3 liquid C12H22O11, aqueous CH2H3O2, and aqueous NH4OH were considered weak electrolytes because these solutions slightly dissociated in water and did not have many moving ions, although there were some solutions that had a brighter red glow than others, they are considered weak because only the red glow was on. Solid NaCl and solid CaCO3 were considered as non-electrolytes because they had no free ions moving and besides that, these two solutions conducted no light. The type of particles that do strong electrolytes are soluble substances as well as some strong acids, weak electrolytes are slightly soluble and these solutions do not completely ionized as strong electrolytes. Now, non-electrolytes are substances that are not dissolved or do not dissolve in water meaning that do not produce any ions. Part II Reactivity of Aqueous Solutions: Typical Chemical Reactions and Net Ionic Equations A. Reaction between 0.1 M HC2H3O2 and 0.1 M NH4OH For this part of the experiment, the electrical conductivity readings 0.1M HC2H3O2 showed a red glow as well as 0.1M NH4O, indicating that it was a weak electrolyte. Now, when these two solutions were mixed together, it showed both red and green glow, indicating that it

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was a strong electrolyte. When mixing, the results indicated that two weak solutions can be mixed together to raise the conductivity of the solutions, this may be due to the fact that solutions react to become stronger. The net ionic equations indicated that in the chemical reaction those ions were the ones that were moving, meaning the ones that were involved. Once the reaction had occurred, the results indicated that the type of reaction that occurred was a double displacement reaction. B. Reaction Between H2CO3 and Saturated Ba(OH)2 Solutions In this part of the experiment, the electrical conductivity of distilled water showed a dim red light similar to the one that was collected in part I in this part of the experiment. However, after blowing CO2 the solution started to show a brighter red glow indicating that when CO2 was added to water it had a greater conductivity. Now, the electrical conductivity of 0.1M Ba(OH)2 solution showed a red and green glow indicating that 0.1M Ba(OH)2 has a strong electrolyte. However, when CO2 was bubbled into 0.1M Ba(OH)2 solutions, it changed from glowing red and green light to only glowing red light. This indicated that the strong electrolyte could be reduced by adding CO2. The net ionic equations were then determined and resulted in Ba2+ (aq) + 2OH(aq) + CO2(g) → BaCO3(s) + H2O(l) in net ionic equations spectator ions should be removed, however, in this specific equation, there are no spectator ions as it forms solid solutions (s) and water liquid (l). This reaction showed that the water was extracted from the reactants and the reaction resulted in a double displacement reaction. The solubility rules were used to determine what type of reactions it was because they indicated if the product was soluble or not. The type of product was easily determined since it involved the exchange of ions and cations. Conductivity is important when predicting the type of reaction and in writing net ionic equations because it will indicate whether the reaction is weak, strong, or non-electrolyte.

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PART III Conductivity of Household/Commercial Products In this part of the experiment, some commercial products were used, and by using the conductivity apparatus the products were classified as strong electrolytes, weak electrolytes, and non-electrolytes. The commercials that showed strong electrolytes were baking soda, 5% Dextrose intravenous (IV) solutionGatorade, or any energy drink these are considered strong electrolytes because they show both, green and red glow. The commercial product that showed weak electrolytes was only vinegar this was considered a weak electrolyte because it had only a red glow. And the product that showed weak electrolyte was rubbing alcohol this was considered as non-electrolyte because it had no glow at all. Although Gatorade has sugar (glucose) it is considered a strong electrolyte because it contains various ions such as K+, Na+, Mg2+, as well as other ions. A practical application of the electrolytic properties of substances in solutions is that it shows whether is soluble or not by using the solubility rules also it shows the degree of conductivity and by using that information the right substance can be then picked according to the need of it. III. Conclusions After the experiment, one can conclude that electrolytes depended on whether the solution is soluble, slightly soluble, or not soluble when mixed with water because the ions of an element or compound will be moving around conducting electricity. One can say that the electric conductance of aqueous solutions was mostly shown as weak electrolytes because the bulb only showed a red glow. However, some exceptions were HCl, NaCl, and Ca(NO3)2 because these show both green and red indicating that it was a strong electrolyte. The electrical conductivity of solid compounds was interfered to be non-electrolytes due to the fact that they are in their solid-state and they are not dissolved in water and therefore the ions were not able to be free.

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Strong conductivity led to the strong electrolyte as the ions were free and completely dissolved in the solvent, the weak electrolytes are slightly soluble and therefore not letting the ions be completely free and the non-electrolytes are the solutions that are not dissolved in a solvent or are compounds that do not have any ions moving around. The major factors that affect the ability to conduct electricity were the ability to completely or slightly dissolved in a solvent that way, ions could be able to dissociate. In the second part of the experiment, electrical conductivity interfered as evidence of a chemical reaction since the conductivity test results and solubility rules were used to identify the formulas and the products that were formed and whether or not it was soluble or insoluble. It was also helpful to identify the type of reaction that occurred after the experiment. The electrical conductivity test proves the occurrence of a chemical reaction because it indicates how a chemical reaction is happening. At the end of this experiment, some lab techniques that were learned in this experiment were how to properly use the conductivity apparatus, and predicting types of reactions that were formed by using the conductivity test. The outcome of the experiment showed similar results from what was expected. A practical application from this experiment could include that if one whats to know how a chemical reaction occurred, the conductivity test can be conducted to determine if there was an actual chemical reaction.

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References CK-12 Foundation. (2018). Physical Properties of Ionic Compounds. Retrieved October 24, 2018, from. https://www.ck12.org/chemistry/physical-properties-ofionic-compounds/lesson/Physical-Properties-of Ionic-Compounds-CHEM/ New Jersey City University. (2013). CHEM 1105: General Chemistry I laboratory and recitation: miniscale experiments. Boston, MA: Pearson Learning Solutions. New Jersey City University. (2021). Department of Chemistry Manual. Properties and Reactivity of Aqueous Solutions. Timberlake, K. (2006). Chemistry laboratory manual: An introduction to general, organic, and biological chemistry. Upper Saddle River, NJ: Pearson Education, Inc. Tro, N. (2017). Chemistry: A molecular approach, 4th Edition. Boston, MA: Pearson.

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