Copy of Unit 5 Sample Work_Chemistry A

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Chemistry

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Dec 6, 2023

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Unit 5A (Gasses) Click File and Make Copy in order to create your own copy to type on. Save as a PDF or Word doc to submit to the drop box. Sample Work is worth 10 points. You will earn 10 points if you answer all the questions and 5 points if you answer some of the questions. Test essay questions are not considered Sample Work. Make sure I can clearly see your answers. Highlight, underline or change the font color to indicate your answer. You may not be able to answer the questions until you have completed the entire unit. The ideal gas law is PV = nRT. Explain what each variable is in this equation and include a common unit used to measure that variable Variable P V n R T Property Pressure Unit Pa/bar/atmosphere In a sealed bottle, the temperature is raised from 200 K to 400 K. What happens to the remaining quantities Pressure (P) ( doubles / halves / stays constant ) Volume (V) ( doubles / halves / stays constant ) Moles (n) (doubles / halves / stays constant ) Gas constant (R) (doubles / halves / stays constant ) Temperature (T) ( doubles / halves / stays constant ) A life raft containing 200 g of air has another 200 g of air added. What happens to the remaining quantities Pressure (P) (doubles / halves / stays constant ) Volume (V) (doubles / halves / stays constant ) Moles (n) ( doubles / halves / stays constant ) Gas constant (R) (doubles / halves / stays constant ) Temperature (T) (doubles / halves / stays constant ) Two quantities in the ideal gas equation that are directly proportional: pressure and volume. [When one increases, the other generally increases, provided the other variables are constant. ]

Two quantities in the ideal gas equation that are indirectly proportional: Pressure and Volume [ When one increases, the other generally decreases, provided the other variables are constant. ] Given that R= 0.0821(L⋅atm) / (mol⋅K) how many moles must be in a 2L container at 1.8 atmospheres with a temperature of 270K? There must be approximately 0.1628 moles of gas in the 2 L container at 1.8 atmospheres and 270 K. Essay Questions: Please answer the following short answer questions on the exam instead of the questions shown on the test itself. Use 3-5 sentences to explain your thinking. Answer all parts of the question to the best of your ability. PUT YOUR ANSWERS ON THE TEST! If you only submit them as part of the Sample Work you will not earn credit on the test. Responses found on the internet (Brainly, Wikipedia, Khan Academy, Course Hero, etc) will automatically be scored as zero and will receive a written Honor Code Violation. Question 1: (answer in place of item 14) A gas at 300 K and under 1 bar of pressure takes up 1.2 L of volume. The gas is quickly compressed to 9 bars and the new temperature is measured to be 1200 K. Use the combined gas law to calculate the new volume of the gas. Show your work! To calculate the new volume of the gas using the combined gas law, we can use the equation: (P1 * V1) / (T1) = (P2 * V2) / (T2) Where: P1 and T1 are the initial pressure (in bars) and temperature (in Kelvin). V1 is the initial volume (in liters). P2 and T2 are the final pressure (in bars) and temperature (in Kelvin). V2 is the final volume (which we want to calculate). Given: P1 = 1 bar T1 = 300 K V1 = 1.2 L P2 = 9 bars T2 = 1200 K

Now, we can solve for V2: (1 bar * 1.2 L) / (300 K) = (9 bars * V2) / (1200 K) (1.2) / (300) = (9 * V2) / (1200) V2 = (1.2 * 1200) / (9 * 300) V2 = 120 / 3 V2 = 40 L The new volume of the gas is 40 liters. Question 2: (answer in place of item 15) Explain one assumption made by treating a gas as ideal. What would be the consequences if this assumption turns out to be untrue? One assumption made when treating a gas as ideal is that there are no intermolecular forces or attractions between gas particles. The consequences of this assumption being untrue would be that the gas behaves differently from ideal behavior under certain conditions. For example, at very high pressures or low temperatures, real gases may deviate from ideal behavior due to molecular interactions. If the assumption of ideal behavior is untrue, it may affect the accuracy of predictions and calculations using the ideal gas law. Question 3: (answer in place of item 16) Two identical pressure cylinders show the same pressure on the gauge. They both are at room temperature. One contains methane (CH 4 ) and the other contains Nitrogen (N 2 ). Can you definitely tell which is which by weighing the cylinders? Why or why not? You cannot definitely tell which cylinder contains methane (CH4) and which contains nitrogen (N2) by weighing the cylinders alone. The reason is that both gases have the same number of molecules for a given volume under the same conditions of temperature and pressure. The ideal gas law (PV = nRT) tells us that the weight of the gas depends on the number of moles (n) and the molar mass (M) of the gas. Since both cylinders are at room temperature and show the same pressure, they contain the same number of moles of gas. Without additional information, such as the molar masses of the gases, you cannot distinguish them based on weight alone. Question 4: (answer in place of item 17) 2 moles of Sodium Azide (NaN 3 ) produces about 3 moles of Nitrogen (N 2 ) in a car's airbag. How many moles of NaN 3 are needed to fill a 65 gram airbag? Assume the gas is produced at a temperature of 30 °C and 2.5 atm. (How many moles of NaN 3 must be extracted from 65 grams of N 2 ?) Id we w find the specific moles of NaN3 needed, you will need to determine the volume (V) of the airbag using the ideal gas law, as the volume is currently unknown. Once you calculate V, you can calculate n(NaN3). Without knowing the value of V, we cannot provide a numerical answer for the moles of NaN3 needed. Extra Credit: How many grams of NaN 3 are needed here?

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