Ionic And Covalent Compounds Lab 3 Lab Instructions PDF

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WEEK 3, LAB 3 OUT OF 9...

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CHEM120: Week 2 lab Name:

Laboratory 3: Ionic and Covalent Compounds Learning Objectives: ● ● ●

Name ionic and covalent compounds and derive their chemical formulas Observe absorption spectra of metal ions using flame test Draw Lewis structures of simple covalent compounds

In this laboratory exercise, we will learn how to derive formulas of ionic and covalent compounds and name them. We will also flame test for various metal ions and make models of simple covalent molecules. Notes: ● ● ● ● ● ● ● ● ●

Read the lab before coming to class. The expectation at Chamberlain (CCN/CU) is that you come to class fully prepared for lab. This lab will involve the use of acids and burners. Be careful and mindful of your surroundings as you handle the chemicals and burners. Always check with your instructor regarding proper waste disposal Listen carefully to the professor’s instructions and work safely Always follow the rules outlined in the safety contract If in doubt of how to use a piece of lab equipment, as you instructor. Improper use of lab equipment can be dangerous or could damage lab materials. If you have any safety concerns, see your instructor. Always dress properly for lab. Be sure to wear closed toed shoes and long pants to lab. In lab, ware your safety equipment including goggles, lab coat, and gloves. Use deionized water (DI water) in your experiments.

Exploration 1: Explain the following terms (Complete prior to class). Cation: A positive ion Anion: A negative ion Ionic bond:

A bond between a nonmetal + metal

Polar covalent bond: between two atoms

A type of chemical bond where a pair of electrons is unequally shared

Nonpolar covalent bond: with each other.

A type of chemical bond where two atoms share a pair of electrons

Hydrogen bond: A weak bond between two molecules resulting from an electrostatic attraction between a proton in one molecule and an electronegative atom in the other.

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CHEM120: Week 2 lab Name: Exploration 2: Ionic compounds Ionic compounds are hard, brittle and crystalline in nature. Ionic compounds have high melting points compared to covalent compounds. Many Ionic compounds are water soluble and conduct electricity. It is possible to identify a compound as an ionic compound or a covalent compound by observing properties such as melting point, solubility and ability to conduct electricity. These properties are due to the nature of the ionic bond. Ionic compounds are made between oppositely charged ions- a cation and an anion. The cation may be a positively charged polyatomic ion or a metal ion. The anion may be a negatively charged polyatomic ion or a nonmetal ion. In this activity, we will learn about naming ionic compounds and deriving their chemical formulas.

Part 2A: Cations and their names Metals form cations by donating electrons in their valence shell to satisfy the octet rule. The name of a cation is the same as name of the element. Complete Table 1 by providing names of cations, their chemical symbols and charges. Table 1: Number Name of Element 1 Lithium 2 Calcium 3 Sodium 4 Aluminum 5 Barium 6 Rubidium 7 Iron 8 Iron 9 Copper 10 Copper

Chemical symbol of the element Li Ca Na Al Ba Rb Fe2 Fe3 Cu1 Cu2

Name of the cation Lithium ion Calcium ion Sodium ion Aluminum ion Barium ion Rubidium ion Iron (II) Iron (III) Copper (I) Copper (II)

Chemical symbol and charge of the cation Li+ Ca2+ Na+ Al3+ Ba2+ Rb+ Fe2+ Fe3+ Cu+ Cu2+

Part 2B: Anions and their Names Non-metals form anions by accepting electrons to complete their valence shell and satisfy the octet rule. The name of an anion is never the same as the name of the element, but rather is named by adding the suffix –ide. Complete Table 2 by providing names of anions, their chemical symbols and charges. Table 2: Number Name of Element 1 Oxygen 2 Sulfur 3 Fluorine

Chemical symbol of the element O S F

Name of the anion Oxide Sulfur Fluoride

Chemical symbol and charge of the anion O-2 S-2 F-1 2

CHEM120: Week 2 lab Name: 4 5 6 7 8

Chlorine Iodine Bromine Nitrogen Phosphorus

Cl I Br N P

Chloride Iodide Bromide Nitride Phosphide

Cl-1 I-1 BR-1 N3P3-

Part 2C: Polyatomic ions and their Names As the name suggests, the polyatomic ions are cations or anions that contain more than one element. Complete Table 3 by providing names of polyatomic ions, their chemical symbols and charges. Table 3: Number 1 2 3 4 5 6 7 8 9 10

Name of Polyatomic Ion Ammonium Hydronium Nitrite Nitrate Cyanide Hydroxide Bicarbonate Carbonate Sulfate Phosphate

Chemical Symbol and charge NH4+ (+1) H3O+ (+1) NO2- (-1) NO3- (-1) CN- (-1) OH- (-1) HCO3- (-1) CO3^2- (2-) SO4^2- (2-) PO4^3- (3-)

Part 2D: Naming Ionic compounds To name an ionic compound, the names of the cation and the anion are combined and the following rules are applied. Rule 1: The name of the cation is always written first. The anion is written second. ●

For example, in an ionic compound containing sodium (cation) and chlorine (anion), sodium will be written before chlorine.

Rule 2: Name of the cation does not change. ●

For example, in an ionic compound containing sodium (cation) and chlorine (anion), name of sodium will be written as is.

Rule 3: Name of the anion is altered by adding the suffix -ide. ●

For example, in an ionic compound containing sodium (cation) and chlorine (anion), chlorine will be altered by adding the suffix –ide and change to chloride.

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CHEM120: Week 2 lab Name: Rule 4: Names of the polyatomic ions do not change. ●

When an ionic compound contains a polyatomic ion, the name does not change. For example, o Aluminum sulfate o Ammonium chloride

Rule 5: Charge of the transition metal ion is indicated as roman numerical in a parenthesis next to the name of the metal. ●

Transition metal ions can have different charges. The charge of a metal ion is indicated as a roman numerical next to the name of the metal ion. For example, o In Iron (II) oxide, Iron has charge of +2 o In Iron (III) oxide, Iron has charge of +3

Derive the names of the ionic compounds based on the rules discussed above and complete Table 4. Table 4: Number 1 2 3 4 5 6 7 8 9 10

Ionic Compound Comprised of: Lithium and Bromine Calcium and Sulfur Potassium and Nitrogen Magnesium and nitrate Ammonium and hydroxide Iron(II) and sulfate Iron(III) and chlorine Copper (I) and phosphate Copper (II) and hydroxide Aluminum and oxygen

Name of the Ionic Compound LiBr (Lithium Bromide) CaS (Calcium Sulfur) K3Na (Potassium Nitride) Mg3N2 (Magnesium Nitrate) (NH4)OH (Ammonium Hydroxide) FeS2 (Iron (II) Sulfur) FeCl3 (Iron (III) Chloride) Cu3-PO4+ Cu-OH2+ Al2-O3+

Part 2E: Deriving chemical formulas of Ionic compounds In the previous section, we learned about naming ionic compounds. In this activity, we will learn to derive the chemical formulas of ionic compounds. In order to derive chemical formulas, we will follow the following steps. Step 1: Write the charge and chemical symbol of cation. If sodium is cation, Chemical symbol for sodium is: Na Charge of sodium is: +1 Therefore, sodium the cation is written as: Na+1 

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CHEM120: Week 2 lab Name: Step 2: Write the charge and chemical symbol of the anion. If chlorine is anion, Chemical symbol for chlorine is: Cl Charge of chlorine is: -1 Therefore, the chlorine anion is written as: Cl-1  Step 3: Ionic compounds are neutral and do not have any net charges. To derive chemical formula, the cation and anion are used in quantities that will neutralize the charges. The chemical formulas for such compounds are generated by combining the symbols of both ions and neutralizing any charge difference by crisscrossing the charges and writing them as subscripts (indicating the number of atoms for each element). This is called the crossover method. Subscripts now indicate the quantities of the cations and anions in a compound.

When the charges are equal in quantity or if charge is equal to +1 or -1, they are not written as shown in the example above. When charges are not equal, the charges are crisscrossed and written. For example, a compound made of calcium and chlorine would be written as follows.

Complete the Table 5 by deriving the chemical formulas. Table 5: Numbe r 1

Ionic Compound Comprised of:

Formula of the Ionic Compound

Sodium and iodine

NaI

2 3 4 5

Barium and phosphate Calcium and sulfate Magnesium and phosphorus Ammonium and phosphate

BaP CaS MgP NH3PO4-

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CHEM120: Week 2 lab Name: 6 7 8 9 10

Iron(II) and Bromine Iron(III) and Chlorine Copper (I) and oxygen Copper (II) and hydroxide Aluminum and oxygen

Fe2Br Fe3Cl Cu2O CuOH2Al2O3

Exploration 3: Covalent compounds Covalent compounds are formed by sharing electrons. Unlike ionic compounds, covalent compounds are soft, squishy, or powdery in nature. Generally, covalent compounds have lower melting points compared to ionic compounds. Covalent compounds dissolve more easily in solvents such as ethanol compared to water. They are weaker in conducting electricity because they do not create ions. Covalent compounds are formed between two nonmetals. The chemical formula of a covalent compound is derived in the same manner as for an ionic compound. Part 3A: Naming Covalent compounds and deriving chemical formula To name a covalent compound, the names of the nonmetal elements are combined and the following rules are applied. Rule 1: The name of the less electronegative (treated like a cation) is always written first. The more electronegative ion (treated like an anion) is written second. ●

For example, in a covalent compound containing phosphorus and chlorine, phosphorus will be written before chlorine as it is less electronegative.

Rule 2: Name of the cation does not change. ●

For example, in a covalent compound containing phosphorus (cation) and chlorine (anion), the name of phosphorus will be written as is.

Rule 3: Name of the anion alters by adding the suffix -ide. ●

For example, in a compound containing phosphorus (cation) and chlorine (anion), name of chlorine will be altered by adding the suffix -ide. The name of chlorine will change to chloride.

Rule 4: The number of each participating atoms are indicated by prefixes mono- (one), di- (two), tri(three), tetra-( four), penta- (five), hexa- ( six), etc. It is common to leave off the prefix mono-. ●

For example, if the compound contains one atom of phosphorus and 5 atoms of chlorine, the name of the compound will be phosphorus pentachloride.

Rule 5: The prefix mono- is used to indicate the difference between two compounds that contain the same elements but in different quantities. ●

For example, the name of CO2 is carbon dioxide. There is no need to write it as monocarbon dioxide to show presence of one atom of carbon. However, CO is named as carbon monoxide to show different quantity of oxygen atoms compared to CO2.

Based on the information given here, complete the Table 6.

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CHEM120: Week 2 lab Name: Table 6: Numbe r 1 2 3 4 5 6 7 8

Chemical Formula

Name of the Covalent Compound

N2O4 SCl2 P4 S3 N2O S2F2 I2 O5 BrF3 HF

DiNitrogen tetroxide Sulfur diChloride tetraphosphorus trisulfide DiNitrogen monoxide disulfate difluoride diIodine penta-oxide Bromine trifluoride Hydrogen monofluoride

To derive the chemical formula of the covalent compound, identify the quantities of participating atoms and write those as subscripts next to the chemical symbol of the element. For example, sulfur hexafluoride indicates that one atom of sulfur (S) and six atoms of fluorine (F) are present in one molecules of sulfur hexafluoride. Therefore, its formula will be SF6. Complete the following table (Table 7) by deriving chemical formulas of covalent compounds based on the name of the compound. Table 7: Numbe r 1 2 3 4 5 6 7 8

Name of the Covalent Compound

Chemical Formula

Dihydrogen sulfide Tricarbon dioxide Carbon dioxide Dichlorine penta-oxide Diphosphorus pentasulfide Nitrogen trichloride Disulfur decaflouride Tetraphosphorus trisulfide

H2S C3O2 CO2 Cl2O5 P2S5 NCl3 S2F10 P4S3

Exploration 4: Flames Test- Identifying the Cation Different metal ions generate a certain colored flame when burned in the blue flame because electrons of metals move to higher energy states. When the electrons return to their normal energy states, the energy is given off in the form of a photon. In many cases, this photon can be observed as visible light. This gives each metal a unique colored flame. In this exploration, we will test different cations (solution or solid) for the color of the flame. We will also test an unknown metal for the color of the flame. Materials: Solids or 1 M solutions of lithium chloride (LiCl), potassium chloride (KCl), copper sulfate (CuSO4), calcium chloride (CaCl2), sodium chloride (NaCl), 1M hydrochloric acid (HCl), DI water, metal loop, burner Method: 1. Obtain a metal loop and a burner. Turn the burner on. Adjust it to have mostly blue flame. 2. Clean the metal loop by dipping in 1M hydrochloric acid (HCl) and then burning it in the flame. 7

CHEM120: Week 2 lab Name: 3. Wait 1-2 minutes to cool. 4. Over your waste beaker, place a drop of a metal ion solution such as 1 M lithium chloride on your loop and then put the loop in the flame. a. You may be given solid LiCl instead of solution. If solid salts are given, touch the loop to the solid salt and burn it in the flame. Record the color of the flame. 5. Clean the loop by dipping in HCl and then burning it in the flame. Make sure that the color specific to a metal is completely cleared before testing another salt. a. Use NaCl the last solid/solution as bright flame of sodium may interfere in colors of other metal ions. b. After cleaning with HCl, you may rinse the loop DI H2O and rest it on your desk (clean surface) in between analysis if needed. 6. Repeat the analysis for all cations by repeating steps 2-5. Record the observations in table 8. Table 8: Number Solution ofColor of flame 1 Lithium Hot Pink/Bright Red 2 Potassium White inner flame & orange outer flame 3 Copper N/A Bright orange 4 Calcium 5 Sodium Yellow-orange 6 Unknown Purple/Red Questions: 1. What is the color of the flame of the unknown solution? The unknown solution had a red flame. 2. The unknown contains one of the cations in the table above. Based on the color of the flame, what cation is present in the unknown? Lithium is present. Exploration 5: Appearance and Solubility of Ionic and Covalent Compounds We will now explore the properties of ionic and covalent compounds. In general, ionic compounds tend to be hard and crystalline in nature, whereas covalent compounds tend to be soft, squishy, or powdery in nature. In terms of solubility, due to their polar nature, ionic compounds tend to dissolve readily in water as the polar bonds of the water molecules allow them to surround the dissociated ions with by partial positive or negative charges. On the other hand, ionic compounds dissolve less readily in nonpolar organic solvents, as there are no partial positive or negative charges to balance out the dissociated ions. Covalent compounds tend to dissolve readily in nonpolar organic solvents and less readily in water. Please note that some organic compounds are also soluble in water if they contain polar bonds such as those found in OH groups. Materials: weigh plates, CaCl2, NaCl, sucrose, stearic acid, 8 test tubes, test tube holder, spatula, water, ethanol, and parafilm.

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CHEM120: Week 2 lab Name: Method: 1. Collect a small sample of each of the four compounds on labeled weighing dishes. 2. Observe the appearance of each of the compounds and record your observations into Table 9. 3. Label two test tubes with the name of each compound and fill one with 5 ml of water and the other with 5 ml of ethanol. 4. Transfer a small, equal amount of CaCl2 into the pair of appropriately labeled test tubes. If a sample rapidly dissolves in the solvent, it is soluble in that solvent. 5. If the sample is not dissolving in a given solvent, parafilm the top of the test tube and shake for 30 seconds to see if any additional dissolution is observed. If the solution begins to dissolve, it is partially soluble in that solvent, if it does not dissolve; it is insoluble in that solvent. 6. Record your solubility observations into table 9. 7. Repeat steps 4-6 for each of your compounds. 8. Retain test tubes containing compounds dissolved in water. Dispose of other materials according to your instructor’s directions. Table 9: Name of Compound

Appearance of compound

Solubility in Water (soluble, partially soluble, or insoluble)

Solubility in Ethanol (soluble, partially soluble, or insoluble)

Based on your observations, is this compound Ionic or Covalent?

NaCl Sucrose

Fine Grate

Soluble

soluble

ionic

Solid grate

soluble

soluble

ionic

Stearic Acid CaCl2 Questions: 1. Based on the appearance of the compounds, which would you expect to be ionic and which would you expect to be covalent? CaCl2 is a nonmetal + metal so I expected it to be covalent. 2. Based on the results of the solubility study, which compounds do you expect to be ionic and which compounds do you expect to be covalent. We were lacking in resources for elements so we only had Sucrose and CaCl2. We could not experiment with the other compounds.

Exploration 6: Conductivity of Ionic and covalent compounds As we discussed in the last section, ionic compounds tend to be soluble in water and separate into ions. These ionic compounds that dissolve in water are known as electrolytes. The ions are good conductors of

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CHEM120: Week 2 lab Name: electricity and thus solutions made from ionic compounds dissolved in water tend to have good conductivity. On the other hand, covalent compounds are less likely to be soluble in water, and those that do dissolve in water do not produce these ions. Therefore, solutions made of covalent compounds and water tend to be poor conductors. Using this information, we will use conductivity measurements to help us determine which of our compounds are ionic and which are covalent. Materials: Water soluble compounds from Exploration 5 and a conductivity meter Method: 1. Check with your instructor for how to use the conductivity meter 2. Measure the conductivity of each of your water based solutions 3. Record your observations in table 10. Table 10: Name of Compound Sucrose

Conductivity 210 ms/cm

Based on your conductivity, is this compound Ionic or Covalent? more conductive/covalent

CaCl2

18.05 ms/cm

less conductive/ionic

Questions: 1. Do your identifications of the compounds as ionic or covalent from the conductivity study match the results from Exploration 5? If not, which ones do not match? Yes, they do match. Both ionic compounds and won’t change because of the elements. 2. Based on the results of both Explorations 5 and 6, which of your substances are ionic and which are covalent. Looking at the results its seen that CaCl2 is ionic and sucrose is covalent. Exploration 7: Draw Lewis structures of simple ionic and covalent compounds Lewis symbols, also known as electron-dot symbols are used to show the number of valence electrons of the main group elements. Valence electrons are placed arou...