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Experiment 6 Determination of a Chemical Formula 43 QUESTIONS PRE LAB 1. A sample of a compound made entirely from copper and oxygen was found to have a total mass of 0.1431 g. The mass of the copper in the compound was found to be 0.1271 g. a. Calculate the number of moles of copper in the sample. b. Calculate the mass of oxygen in the sample.

c. Calculate the number of moles of oxygen in the sample. d. Use the mole ratio of copper to oxygen rounded off to the nearest whole number to determine both the formula and the molar mass of the compound.

PRE LAB 1. List three specific safety instructions that are relevant to this lab. 2. List three observations that might suggest that a chemical reaction has occurred. 3. What observation would you expect to make when red litmus paper is exposed to a basic solution? 4. What is another word for a solid that is produced from the chemical reaction between two aqueous solu- tions?

50 Experiment 7 Types of Chemical Reactions QUESTIONS POST LAB 1. In experiment #3, the manganese dioxide (MnO₂) was added to the test tube containing hydrogen peroxide (H₂O₂) in order to speed up the reaction. What is the name given to a chemical that is added to a reaction in order to increase its rate? 2. Did you expect tap water to be acidic, basic or neither? Explain your answer.

2. Did you expect tap water to be acidic, basic or neither? Explain your answer. 3. Neutralization reactions involve the hydrogen ions (H+) from an acid, reacting with a base that often contains hydroxide ions (OH). Use this information to predict the name and formula for the chemical substance that is always produced in this type of reaction.

56 Experiment 8 Ideal Gas Law: Estimation of Molar Mass of Magnesium QUESTIONS PRE LAB A 0.0500-g sample of magnesium is reacted with 25 ml of 3.0 M sulfuric acid as described in the e tal section. The resulting hydrogen gas is collected over water and is found to have a volume of 51. temperature is 25 °C and the atmospheric pressure is 760.00 mm Hg. The column of water height graduated cylinder is found to be 24.0 mm. 1. What is the height of the water column after converting to an equivalent height of mercury 2. What is the pressure of the hydrogen gas in the column in mm Hg? 3. What is the pressure in question 2 converted to atmospheres? 4. What is the number of moles of hydrogen gas in the sample? 5. What is the number of moles of metal in the sample? 6. What is the calculated molar mass of the metal for this trial? 7. What is the percent error in this determination?

56 Experiment 8 Ideal Gas Law: Estimation of Molar Mass of Magnesium QUESTIONS PRE LAB A 0.0500-g sample of magnesium is reacted with 25 mL of 3.0 M sulfuric acid as described in the experimen- tal section. The resulting hydrogen gas is collected over water and is found to have a volume of 51.0 mL. The temperature is 25 °C and the atmospheric pressure is 760.00 mm Hg. The column of water height inside the graduated cylinder is found to be 24.0 mm. 1. What is the height of the water column after converting to an equivalent height of mercury in mm? 2. What is the pressure of the hydrogen gas in the column in mm Hg? 3. What is the pressure in question 2 converted to atmospheres? 4. What is the number of moles of hydrogen gas in the sample? QUES POST A 0.05 tal sect temper gradua 1. 5.

4. What is the number of moles of hydrogen gas in the sample? 5. What is the number of moles of metal in the sample? 6. What is the calculated molar mass of the metal for this trial? 7. What is the percent error in this determination?

Experiment 8 Ideal Gas Law: Estimation of Molar Mass of Magnesium 57 QUESTIONS DIRECTO POST LAB A 0.0524-g sample of magnesium is reacted with 25 mL of 3.0 M sulfuric acid as described in the experimen- tal section. The resulting hydrogen gas is collected over water and is found to have a volume of 53.6 ml.. The temperature is 25 °C and the atmospheric pressure is 762.12 mm Hg. The column of water height inside the graduated cylinder is found to be 22.9 mm. 1. What is the height of the water column after converting to an equivalent height of mercury in mm? 2. What is the pressure of the hydrogen gas in the column in mm Hg? 3. What is the pressure in question 2 in atmospheres? 4. What is the number of moles of hydrogen gas in the sample?

5. What is the number of moles of metal in the sample? 6. What is the calculated molar mass of the metal for this trial? 7. What is the percent error in this determination?

QUESTIONS PRE LAB 1. How would the calculated concentration of the HCl be affected, if the sodium hydroxide were poured from a beaker that contained some water before the NaOH were added to it? 2. What color is phenolphthalein in acid? What color is it in base? 3. The acid and base in this experiment are completely harmless-True or False? Explain your answer.

QUESTIONS POST LAB 1. What color did you see at the end-point of the titration when using phenolphthalein? 2. If significantly less then 25.00 mL of acid were added to the flask in step 7 of the Procedure, what affect would this have on the accuracy of the sodium hydroxide concentration? Explain your answer. 3. What volume of 0.200 M sodium hydroxide is required to completely neutralize 50.00 mL of 0.199 M hydrochloric acid?

POST LAB 1. How do you recognize that two molecules are indeed isomers? 2. What is the difference between a molecular formula and a structural formula? 3. Draw four structural formulas for the isomers of C,H,Cl.

4. What do all of the isomers in question 3 have in common? 5. Draw four isomers all having the molecular formula C,H₁4. Use structural formulas and name them. 6. Explain why Butane does not have a cis or trans isomer, while 2-Butene does have a cis and a trans isomers.

Experiment 11 Some Organic Functional Groups 77 QUESTIONS POST LAB 1. Write molecular formulas for all of the above compounds and identify any isomers.

2. Name the compounds above which will have a pH below 7.