Expert Answers

Description Suppose you had a buffer containing 0.5 moles of sodium monobasic phosphate and 0.5 moles of sodium dibasic phosphate. How many moles of hydrochloric acid would this phosphate buffer be able to accept before the pH of the solution began to change drastically

Description 11  a 3.00 L flexible container holds a sample of hydrogen gas at 153kPa if the pressure increases to 203kPa and the temperature remains constant what will the volume be? 4.50L 0.22L 0.44L 2.26L 12  12 a 3.0L container holds a sample of hydrogen gas at 300K if the temperature decreases to 100K and the pressure remains constant what will the volume be? 1.0L 0.1L 9.0L 0.3L 13 you compare the gas generated from a reaction using 2 antacid tablets with the gas generated from a reaction  using 4 antacid tablets (consider the antacid to be the limiting reagent) at constant pressure and temperature how do the volumes of the gases compare? the gas generated by 4 antacid tablets has a greater volume the 2 reactions produce the same amount of gas the gas generated by 2 antacid tablets has a greater volume 14  a 1.0 L container holds a sample of hydrogen gas a 300 K and 101.5kPa if the pressure increases to 508k Pa and the volume remains constant what will the temperature be? 901K 103K 1,501K 605K 15 which of the following is the mathematical representation of Charles law? V1l T1=V2l T2 P1V1=V2l T2 P1l T1= P2l T2 P1V1=P2 V2  the following question was on a quiz   you fill a tank with gas at 60C to 100kPa and seal it you decrease the tempersture to 10 C but keep the volume constant what happens to the pressure? a student answers that the new pressure will be 17kPa which of the following explanations is true? the student did not work with the absolute temperatures, and the answer should be 85kPa the student did not solve for the correct parameter and the answer should be 600kPa the student did not solve for the correct parameter and the answer should be 50kPa the student did not work with aboulute temperature and the answer should be 888kPa 17 a balloon contains 2.0L of air at 101.5kPa you squeeze the balloon to a volume of 0.5 l what is the pressure of the air inside the balloon? 101kPa 406kPa 812kPa 13kPa 18 you place a balloon in a closed chamber at STP when the balloon doubles in size what happens to the chamber pressure? the pressure doubles the pressure stays the same the pressure increases to 4 times the orginal pressure the pressure is reduced by one half 19 in a problem you are given 2 pressures and one temperature at constant volume and amount of gas you are asked to find a second temperature what law should you use? Boyles law Gay Lussacs law charles's law avogadro's law 20 sensors detect the concentration of mercaptan molecules in natural gas at various distances from a leaking source. at which location will a sensor detect the highest concentration of mercaptan one meter in front of the source one meter behind the source one half meter in front of the source two meters behind the source

Description Methanol and toluene are flammable liquids whose vapor pressures at 68ºF (20ºC) are 96 and 22 mmHg, respectively. Based solely on this data, determine which compound poses the greater risk of fire and explosion at 68ºF (20ºC). Explain your choice. In general, discuss how vapor pressure affects the volatility of a liquid?

Description Give the main/longest chain name (1pt), functional group(s) name (2pts) and IUPAC name (2pts) of the following organic compound: CH3CH2CH2CH2CH2OH. (Points : 5)       

Description Two liquid compounds, A and B, have the same molecular weight.  Samples of A & B were placed on temperature probes and allowed to evaporate, as in today's experimental procedure.  After 105 seconds, Liquid A had a ?T of 10.2ºC, and liquid B had a ?T of 3.7ºC. 1.  Which of the two liquids required more energy to overcome intermolecular attractions and evaporate?  Explain your reasoning. 2.  Which of the two liquids has higher intermolecular attractions?  Explain your reasoning.

Description One step in the Kjeldahl method for measuring the amount of nitrogen in organic compounds uses a dilute solution of boric acid, H3BO3, in water.  If 150 mL of the boric acid solution contains 16.7 g of boric acid, what is the molarity? Be sure to show ALL work, include units in your work as well as your answer.

Description https://docs.google.com/document/d/1NgeVUvX44_HwU8cX3s6A1hbe2o8BR_Lo6ZuUfMnqtlA/edit 1.)After verifying your data on the Lab assignment, complete the calculations for the density for each trial, and then report the average. Do this for both pre-1981 pennies and post-1983 pennies in the table below. Pre-1981 Pennies Post-1983 Pennies Trial 1 Trial 2 Trial 1 Trial 2 Density g/mL g/mL g/mL g/mL Average Density g/mL g/mL Your results from Part A should have demonstrated that the pennies from these two eras have different compositions. One type of penny is mostly copper (95%) with a thin layer of zinc (5%) while the other penny is mostly zinc (97.5%) with a thin outer layer of copper (2.5%). If the density of copper is 8.96 g/mL and the density of zinc is 7.13 g/mL, determine which penny is which based on your results. Fill in the statements below with "pre-1982" or "post-1982" based on your results. The penny is mostly copper (95%) with a thin layer of zinc (5%). The penny is mostly zinc (97.5%) with a thin layer of copper (2.5%). Write in complete sentences to support your choice based on your experimental data and results. 2.)Based on the data from the video for Density of an Unknown Liquid and a Mixture, calculate the following results below (recall, each liquid was measured to 10.0 mL): Unknown Liquid 50/50 Mixture Mass of liquid g g Density of liquid g/mL g/mL Ethanol (or ethyl alcohol) is the specific type of alcohol present in alcoholic beverages like beer, wine, vodka, etc. When ethanol is added to water, the two liquids mix completely with one another. At room temperature, ethanol’s density is 0.789 g/mL while water’s density is 0.997 g/mL. A student is given an unknown alcoholic beverage in a beaker to analyze at room temperature, so the student puts a piece of ice in the unknown liquid and observes that the ice drops below the surface and floats in the middle of the liquid. Based on this observation above and given ice’s density is 0.917 g/mL, what can you conclude about the density and composition of the liquid? Complete the following with "pure ethanol", "pure water", or "a mixture of the two": The liquid is . If it is a mixture, use density to determine if it contains more ethanol or more water, then write in complete sentences to explain your conclusions. 3.)In your calculation of the density of the unknown liquid (in Part B, question 2 above), which measurement limited the number of significant figures in the reported density: volume or mass? Suppose a student wanted to determine the density with more precision. He decided to retake the mass of the liquid on the analytical balance because he feels this will provide more precision for the experiment. Explain whether or not this an effective approach. 4.)In Part C of the experiment, you determined the density of CO2 gas. You may review this data in the prior assignment. How does the density of CO2 compare to the density of the pennies and the unknown liquid and other solids and liquids included in Table I on page 25? What can you conclude about the density of gases compared to the densities of liquids and solids? Based on the arrangement and number of particles in solids, liquids, and gases, explain why the densities of gases are so different from the densities of solids and liquids. 5.)A substance of higher density will sink in a substance of lower density: For example, you may know that oil floats on top of water because it has a lower density. For each of the following pairs, determine whether the object will sink or float. Refer to Table I on p. 27 and your experimental results to determine each. - a b A balloon filled with air (0.0012 g/mL) in a chamber filled with CO2 (0.0018 g/mL) will - a b A lead brick (11.4 g/mL) placed in a bucket of liquid mercury (13.5 g/mL) will - a b A piece of ice (0.917 g/mL) placed in pure ethanol (0.789 g/mL)

Description Question #1. The wavelength of maximum absorbance from the absorption spectrum for [Fe(SCN)]2+ is: ?max = Question #2. Insert a screenshot of your?absorption spectrum showing your??max? determination here. Question #3.Record the actual volumes of reagents used to prepare Standard Solutions 1 – 4 in Report Table 1. Report Table 1. Reagent volumes used to prepare standard solutions. Standard Solution volume of 0.200 M Fe(NO3)3, mL volume of 0.00200 M KSCN, mL 1 2 3 4 Calculation #1. Calculate the concentration of [Fe(SCN)]2+ in Standard Solution 1, assuming that the SCN– is the limiting reagent. Show your work, including units, below. Enter your calculation result in Report Table 2 below. Question #4. Calculate the concentration of [Fe(SCN)]2+ in Standard Solutions 2 – 4 and enter the results in Report Table 2 below. Also enter the absorbance data measured for Standard Solutions 1 – 4 in Report Table 2 below. Include the wavelength at which you made the measurement. Report Table 2. Absorbance and Concentration of Standard Solutions 1-4. Standard Solution [[Fe(SCN)]2+], M Absorbance at _________ nm 1 2 3 4 Question #5. Insert a screen shot of your calibration plot (standard curve) including the slope, y-intercept, and R2 (correlation) values. Label your axes. Question #6. Complete Report Table 3 below using the actual volumes used to prepare the equilibrium mixtures. Record the volumes to 2 decimal places. Report Table 3. Initial Concentrations of Equilibrium Mixtures A – E. Equilibrium Mixture Fe(NO3)3, mL (________ M) KSCN, mL (________ M) total volume of mixture (mL) A B C D E Question #7. Record the absorbance of each of the equilibrium mixtures in Report Table 4. Note the wavelength used for the measurements. Report Table 4. Absorbances of equilibrium mixtures. Equilibrium Mixture Absorbance at ___________ nm A B C D E DATA ANALYSIS Calculate Concentrations in Equilibrium Mixtures A-E Calculation #2. Calculate the initial concentrations of Fe3+ and SCN– in Equilibrium Mixture A. Show your work, including units, below. Also enter your calculation result in Report Table 5 below. Question #8. Calculate the initial concentrations of Fe3+ and SCN– in Equilibrium Mixtures B – E. Enter your calculation result in Report Table 5 below. Report Table 5. Initial Concentrations of Equilibrium Mixtures A – E Equilibrium Mixture initial Fe3+ (M) initial SCN– (M) A B C D E Calculation #3. Calculate the equilibrium concentration of [Fe(SCN)]2+ in Equilibrium Mixture A by using the absorbance measured for the mixture and the best-fit line from the calibration plot. Show your work, including units, below. Also enter your calculation result in Report Table 6 below. Calculation #4. Calculate the equilibrium concentrations of Fe3+ and SCN– in Equilibrium Mixture A using an ICE table. Show your work, including units, below. Also enter your calculation result in Report Table 6 below. Calculation #5. Calculate the value of the equilibrium constant, K, for Equilibrium Mixture A, by using the equilibrium concentrations of each of the three species in the equilibrium system. Show your work, including units, below. Also enter your calculation result in Report Table 6 below. Question #9. Calculate the equilibrium concentrations of [Fe(SCN)]2+ in the mixtures B – E. (You may use a spreadsheet for these calculations if you wish.) Calculate the equilibrium concentrations of Fe3+ and SCN– of Equilibrium Mixtures A – E, using an ICE table. Calculate a value for the equilibrium constant, K, for each mixture (i.e., by using the equilibrium concentrations of each of the three species in the equilibrium system). Enter your calculation results in Report Table 6 below. Report Table 6. Absorbances, Equilibrium Concentrations, and Values of the Equilibrium Constant for Equilibrium Mixtures A – E Equilibrium Mixture equilibrium [[Fe(SCN)2+]], M equilibrium [Fe3+], M equilibrium [SCN–], M equilibrium constant, K A B C D E RESULTS Calculation #6. Calculate an average value for the equilibrium constant, Kave, and the standard deviation (by using the function =stdev.p(range of K values) in Excel). Values of K can be considered constant if each K value differs from the average by less than 2 times the standard deviation. Average K = _________________ Standard deviation = ___________________ Question #10. Comment on the K values you obtained in this experiment. Can the values you obtained for K be considered constant, according to the criteria (e.g., standard deviation) described above? Support your claim using evidence (i.e., experimental data or results). Are your results consistent with what you’ve learned about equilibrium? Explain your reasoning.

Description Experiment 1 weigh DRY pennies-- tare the weigh paper -- use analytical balances Check the pennies you use to make sure they fall into the correct date range before each trial. Then, KEEP TRACK of the pennies so they REMAIN sorted by date, by placing them into correctly labeled bags. Measure the volume using a 50 mL cylinder. Don't forget to write the decimal places on your measurement, especially if there is a 0. Repeat for 2 trials each-- pre- and post- 1983 pennies. Run the first trial all the way through before starting the second trial. In your calculations, report an EXTRA significant digit in your density. (Underline the last sig fig, and keep one extra.) This will include your measured values in the average, keeping your average as accurate as possible. Only round once, at the very end. To work in pairs, I suggest having one person run one set of pennies and the other person run the other set of pennies. Then you can share data after the trials are complete. Question 1 For Part A, you will measure the volume of a small stack of pennies using volume by displacement (or water displacement), one of the methods used in Experiment 1. Briefly describe how you will use a 50 mL graduated cylinder and water to measure the volume of pennies by displacement. (In your notebook, consider sketching the graduated cylinder and water before and after the pennies are added.) List the measurements you will make and how they will be used to calculate the volume of pennies. Question 2 Consider the data shown below for a rectangular metal sample. A student used an analytical balance and a centimeter ruler marked to every 0.1 cm, and recorded the following: Table 1: Experimental Measurements Mass of Metal Sample 77.51 g Length of Metal Sample 4.5 cm Width of Metal Sample 1.6 cm Thickness of Metal Sample 1.6 cm a. Calculate the density of the metal sample, expressing the final answer with the correct significant figures in the first box, and correct units in the second box. (Use the ^ symbol to indicate a unit raised to a power. For example, x2 would be entered as x^2.) D = b. There are two mistakes in this data, based on the type of instruments used to make the measurements. Identify the mistakes. The mass is recorded incorrectly because . The lengths are recorded incorrectly because: Question 3 You will use a 50-mL graduated cylinder in this experiment to measure volume. Given that smallest marking on this graduated cylinder is 1 mL, circle all of the following sample measurements that are NOT appropriate or NOT recorded to the correct number of decimal places using a 50-mL graduated cylinder: 44.1 mL 32.5 mL 15.11 mL 15 mL

Description Potassium has two naturally occurring isotopes. The masses (amu) and percent abundances of the two isotopes are given below. Show your work, and calculate the average atomic mass of the element in amu units. Name the steps of the scientific method and apply them to an everyday problem you might solve using the method. Be detailed with your answer, and explain each step of your problem. Which of the items below would be considered the densest? (Show your step-by-step work for calculating density of each, in the units of g/mL, to support of your final answer) A piece of wood with a volume of 2.5 L and a mass of 12.5 kg A ball with a volume of 139 mL and a mass of 93 g A tire with a volume of 2.12 L and a mass of 4.22 x 104 mg A wire with a volume of 3.91 x 10-7 L and a mass of 7.93 x 10-1 ng A block of metal with a volume of 1350 mL and a mass of 1.29 x 103 g