SCIN131-Introduction to Chemistry-APUS-Lesson 5 Assignment

Part 1 of 3 - 16.0/ 20.0 Points Question 1 of 12 4.0/ 4.0 Points The vapor pressure of water at 20.0°C is 17.5 mm Hg. If the pressure of a gas collected over water was measured to be 453.0 mm Hg. What is the pressure of the pure gas?  A.0.573 atm  B.0.619 atm  C.0.0230 atm  D.0.596 atm  E.none of the above Answer Key: A Question 2 of 12 0.0/ 4.0 Points What is the third most abundant component of dry air?  A.nitrogen  B.carbon dioxide  C.smog  D.oxygen  E.argon Answer Key: E Question 3 of 12 4.0/ 4.0 Points Divers often inflate heavy duty balloons attached to salvage items on the sea floor. If a balloon is filled to a volume of 3.00 L at a pressure of 2.50 atm, what is the volume of the balloon when it reaches the surface?  A.5.50 L  B.7.50 L  C.0.833 L  D.1.20 L  E.none of the above Answer Key: B Question 4 of 12 4.0/ 4.0 Points What is the temperature (°C) of 2.48 moles of gas stored in a 30.0 L container at 1559 mm Hg? (R= 0.0821 L atm/ mol K)  A.302  B.-84  C.189  D.29  E.none of the above Answer Key: D Question 5 of 12 4.0/ 4.0 Points Suppose you had a balloon containing 1 mole of helium at STP and a balloon containing 1 mole of oxygen at STP. Which statement is TRUE?  A.The balloons will have the same volume.  B.The balloons will have the same mass.  C.Both A) and B) are true.  D.Neither A) nor B) are true.  E.not enough information Answer Key: A

Part 2 of 3 - 16.0/ 20.0 Points Question 6 of 12 4.0/ 4.0 Points Silicon is which type of solid?  A.nonbonding atomic solid  B.metallic atomic solid  C.ionic solid  D.covalent atomic solid  E.molecular solid Answer Key: D Question 7 of 12 4.0/ 4.0 Points A situation where two opposite processes are occurring at equal rates, and no net change is taking place, is called:  A.evaporation.  B.vaporization.  C.dynamic equilibrium.  D.condensation.  E.none of the above Answer Key: C Question 8 of 12 4.0/ 4.0 Points The opposite process of freezing is:  A.boiling.  B.evaporation.  C.condensation.  D.sublimation.  E.none of the above Answer Key: E Question 9 of 12 4.0/ 4.0 Points Increasing the intermolecular forces of a liquid will do which of the following?  A.decrease the vapor pressure  B.decrease the evaporation rate  C.increase the surface tension  D.increase the viscosity  E.all of the above Answer Key: E Question 10 of 12 0.0/ 4.0 Points Which intermolecular forces are found in CO2?  A.dipole-dipole forces  B.dispersion forces and dipole-dipole forces  C.dispersion forces  D.hydrogen bonding  E.none of the above Answer Key: C

Part 3 of 3 - 10.0/ 10.0 Points Question 11 of 12 5.0/ 5.0 Points An experiment shows that a 153-mL gas sample has a mass of 0.171 g at a pressure of 761 mm Hg and a temperature of 32oC. What is the molar mass of the gas? R=0.0821 L atm / mol K Using Ideal gas law PV = nRT 761 mm Hg = 1 atm 153 ml = 0.153 L 32 C = 305 K 1 * 0.153 = n * 0.0821 * 305 n = 0.153/ 25.04  n= 0.006 moles Number of moles = mass/Molar mass 0.006 = 0.171 / M Molar mass = 28.5 Feedback: Gas laws are in Ch 11 Question 12 of 12 5.0/ 5.0 Points Water can be formed according to the equation: 2H2 (g) + O2 (g) → 2H2O (g) If 8.0 L of hydrogen is reacted at STP, exactly how many liters of oxygen at STP would be needed to allow complete reaction? As both gases are in STP  According to Avogadro law, equal volumes of different gasses contains equal number of moles  So mole ratio= volume ratio  VH2:VO2=2:1  If Volume of H2=8.0L  Then Volume of O2=8.0/2 L=4.0L Feedback: Gas Laws are found in Chapter 11

Part 1 of 3 - 20.0/ 20.0 Points Question 1 of 12 4.0/ 4.0 Points The vapor pressure of water at 20.0°C is 17.5 mm Hg. If the pressure of a gas collected over water was measured to be 453.0 mm Hg. What is the pressure of the pure gas?  A.0.573 atm  B.0.619 atm  C.0.0230 atm  D.0.596 atm  E.none of the above Answer Key: A Question 2 of 12 4.0/ 4.0 Points A 3.76 g sample of a noble gas is stored in a 2.00 L vessel at 874 torr and 25°C. What is the noble gas? (R= 0.0821 L atm/ mol K)  A.He  B.Ne  C.Ar  D.Kr  E.not enough information Answer Key: C Question 3 of 12 4.0/ 4.0 Points The initial volume of a gas cylinder is 750.0 mL. If the pressure of a gas inside the cylinder changes from 840.0 mm Hg to 360.0 mm Hg, what is the final volume the gas occupies?  A.1.750 L  B.3.151 L  C.321.4 mL  D.630.0 mL  E.none of the above Answer Key: A Question 4 of 12 4.0/ 4.0 Points Suppose you had a balloon containing 1 mole of helium at STP and a balloon containing 1 mole of oxygen at STP. Which statement is TRUE?  A.The balloons will have the same volume.  B.The balloons will have the same mass.  C.Both A) and B) are true.  D.Neither A) nor B) are true.  E.not enough information Answer Key: A Question 5 of 12 4.0/ 4.0 Points A certain volume of gas was confined in a rigid container. If the pressure of the gas sample in the container was doubled, what happened to the temperature?  A.The temperature became one half.  B.The temperature increased four times.  C.The temperature decreased one-third.  D.The temperature doubled.  E.not enough information Answer Key: D

Part 2 of 3 - 16.0/ 20.0 Points Question 6 of 12 4.0/ 4.0 Points What types of forces exist between I2 molecules?  A.dispersion forces  B.hydrogen bonding  C.ion-dipole forces  D.dipole-dipole forces  E.none of the above Answer Key: A Question 7 of 12 0.0/ 4.0 Points The opposite process of freezing is:  A.boiling.  B.evaporation.  C.condensation.  D.sublimation.  E.none of the above Answer Key: E Question 8 of 12 4.0/ 4.0 Points What happens as you start to add heat to a solid substance?  A.Heating of the now formed liquid results in increasing the liquid temperature.  B.Increasing the rate of heating of a substance at its melting point only causes more rapid melting.  C.When the melting point is reached, the thermal energy is sufficient to overcome intermolecular forces holding the components at their stationary points.  D.Thermal energy causes the components of the solid to vibrate faster.  E.all of the above Answer Key: E Question 9 of 12 4.0/ 4.0 Points Which intermolecular force is present in all molecules and atoms?  A.dispersion forces  B.dipole-dipole forces  C.X-forces  D.hydrogen bonding  E.none of the above Answer Key: A Question 10 of 12 4.0/ 4.0 Points Which compound in liquid form will have the highest vapor pressure?  A.CH4  B.CH3CH2OH  C.CH3CH3  D.CH3C(O)CH3  E.not enough information Answer Key: A

Part 3 of 3 - 10.0/ 10.0 Points Question 11 of 12 5.0/ 5.0 Points Describe (using what you know about gases) why a can of compressed air gets cold after you use it to clean your keyboard. When we compress air (or any gas), its temperature increases. When we dilate it (or lower its pressure), it cools down. That's why a can of compressed air gets really cold when we spray. Question 12 of 12 5.0/ 5.0 Points An experiment shows that a 153-mL gas sample has a mass of 0.171 g at a pressure of 761 mm Hg and a temperature of 32oC. What is the molar mass of the gas? R=0.0821 L atm / mol K By Ideal gas law  PV = nRT  n = PV/RT  P = 761 mm Hg =1 atm V = 153 mL = 0.153  L  T = 32 C =  305 K n = 1 * 0.153 / 0.0821 * 305 n = 0.006   Molar mass = 0.171 / 0.006 = 28.5 g/mole Feedback: Gas laws are in Ch 11

Question 1 of 12 4.0/ 4.0 Points You are working in the lab with gaseous helium at a constant temperature.  You have a 5.00 L tank at a pressure of 1.25 atm.  If the pressure of the tank increases to 2.50 atm, what would you expect to happen?  A.the volume of the gas remains the same  B.the volume of the gas decreases by one-half  C.the volume of the gas increases by one-half  D.not enough information given Answer Key: B Question 2 of 12 4.0/ 4.0 Points The air that we breathe is a combination of many gasses. Which gas is makes up the majority of our air?  A.nitrogen  B.carbon dioxide  C.oxygen  D.smog  E.argon Answer Key: A Feedback: Good. Gas mixtures are discussed in 11.9 Question 3 of 12 4.0/ 4.0 Points You have a 6.75 L container of pure gaseous oxygen at a constant pressure of 1.25 atm. If the temperature is 298 K, calculate the number of grams of oxygen (O2) gas in the container. R = 0.0821 L atm / mol K  A.11.1 g  B.2.90 g  C.0.346 g  D.92.8 g Answer Key: A Question 4 of 12 4.0/ 4.0 Points Which of the following is equivalent to 2.5 atm?  A.1900 torr  B.29.4 psi  C.0.00329 mmHg  D.5.9 psi Answer Key: A Question 5 of 12 4.0/ 4.0 Points You have a fixed container with a volume of 5.00L that contains 35.0 g nitrogen gas (N2).  If the temperature is 298 K, calculate the pressure in the container.  R = 0.0821 L atm / mol K  A.30.6 atm  B.171 atm  C.6.12 atm  D.856 atm Answer Key: C

Part 2 of 3 - 12.0/ 20.0 Points Question 6 of 12 4.0/ 4.0 Points What type(s) of matter has a high density and does NOT take the shape of its container?  A.solids  B.both solids and liquids  C.gases  D.liquids Answer Key: D Feedback: Good. This is discussed in 12.2 Comment: You are correct. I have awarded your points. Question 7 of 12 4.0/ 4.0 Points As a kid, I used to have sleepovers with one of my really good friends. Her dad would bring home dry ice and place it in a bowl in the center of the table. The solid dry ice changed into a gas and flowed over our pizza. What term describes this behavior?  A.sublimation  B.melting  C.deposition  D.condensation  E.evaporation Answer Key: A Question 8 of 12 0.0/ 4.0 Points What type(s) of matter can be described as having a low density and as being compressible?  A.both gases and liquids  B.solids  C.gases  D.liquids  E.both solids and liquids Answer Key: C Feedback: This is discussed in 12.2 Question 9 of 12 0.0/ 4.0 Points The two compounds below have very different boiling points.  What is the most likely reason that compound B boils at a much lower temperature than compound A? Compound A                                             Compound B bp = 148.5*F                                              bp = -4.4*F mw = 32 g/mol                                          mw = 30 g/mol                                In case the images don't display correctly: Compound A is methanol, compound B is formaldehyde.  A.compound A has hydrogen bonding attractions and compound B does not  B.there is no specific reason as both compounds are made up of C, H, and O atoms and have similar molar masses.  C.compound B has hydrogen bonding capability whereas compound A does not.  D.Compound B has dipole -dipole interactions and compound A does not Answer Key: A Feedback: see section 12.6 Question 10 of 12 4.0/ 4.0 Points You calculate the heat of fusion to freeze 1 mol of a solid and get a negative number. What does this mean?  A.You did the calculation incorrectly and need to redo it  B.It is an exothermic reaction  C.It is an endothermic reaction  D.Not enough information given Answer Key: B Feedback: see section 12.5

Part 3 of 3 - 7.0/ 10.0 Points Question 11 of 12 3.0/ 5.0 Points Which compound will have a higher boiling point, HF or HBr? Explain how you know and why, in detail, using the information from the course materials. What is the most prominent intermolecular force present? The order of Boiling point is like this: HF > HBr  Both the elements Florine and Bromine are from same group and when they progress they gets new shells of electrons added up which results in London Dispersion forces. How ever instead of HI, HF shows a greater boiling point in the group. Fluorine has lesser electrons than Chlorine and hence should have lesser London dispersion forces between them. This is true but there is another reason behind that which is Hydrogen Bonding, which is the most prominent inter-molecular force present. Feedback: Intermolecular forces can be found in Chapter 12. Comment: Your answer is correct, but I'm not sure why you mentioned HI and why you're talking about the new shells of electrons. The answer I am looking for is below. Review the material to ensure full comprehension.  HF will have the higher boiling point because of its capability to hydrogen bond with itself. HBr and HF both have dipole-dipole attractions, but only HF can hydrogen bond. They both also have dispersion forces, but the hydrogen bonding will predominate over the increased dispersion forces in HBr due to the increase in molecular weight. Question 12 of 12 4.0/ 5.0 Points If I have a tank that is holding 7.50 L of elemental nitrogen gas with a mass of 250.0 g at a temperature of 58.0 degrees C, what is the pressure? You must show all work to receive credit.   From Ideal Gas Equation, PV = nRT  P = nRT/V  V = 7.50  L  T = 58 C =  331 K  mass = 250 g Molar mass = Mass/n, so n = 250/14 = 17.857 moles P = 17.857*(0.0821)*331/7.50 P = 64.70 atm.  n = 0.006  Feedback: Gas laws are in Ch 11 Comment: You're on the right track. Elemental Nitrogen gas is N2, not just N, so the mass for converting to mols is 28 g/ mol. See below.  Convert to moles first. N = 250g * (1mol/28g) = 8.929 mol  P = nRT/V = (8.929 mol) (0.0821 L atm / mol K) ( 331.35K) / 7.50 L  P=32.4 atm

Question 1 of 12 4.0/ 4.0 Points The vapor pressure of water at 20.0°C is 17.5 mm Hg. If the pressure of a gas collected over water was measured to be 453.0 mm Hg. What is the pressure of the pure gas?  A.0.573 atm  B.0.619 atm  C.0.0230 atm  D.0.596 atm  E.none of the above Answer Key: A Question 2 of 12 4.0/ 4.0 Points How many moles of gas were added to a balloon that started with 2.3 moles of gas and a volume of 1.4 l given that the final volume was 7.2 L?  A.12  B.0.085  C.4.4  D.9.5  E.none of the above Answer Key: D Question 3 of 12 4.0/ 4.0 Points What happens to the volume of a gas when you double the number of moles of gas while keeping the temperature and pressure constant?  A.The volume increases, but more information is needed.  B.The volume is halved.  C.The volume decreases, but more information is needed.  D.The volume doubles.  E.none of the above Answer Key: D Question 4 of 12 4.0/ 4.0 Points A balloon originally had a volume of 0.439 L at 44°C and a pressure of 729 torr. To what temperature must the balloon be cooled to reduce its volume to 378 mL if the pressure remained constant?  A.273°C  B.0°C  C.38°C  D.95°C  E.none of the above Answer Key: B Question 5 of 12 4.0/ 4.0 Points What is the initial temperature (°C) of a system that has the pressure decreased by 10 times while the volume increased by 5 times with a final temperature of 150 K?  A.-198  B.75  C.27  D.300  E.none of the above Answer Key: C

Part 2 of 3 - 20.0/ 20.0 Points Question 6 of 12 4.0/ 4.0 Points Increasing the intermolecular forces of a liquid will do which of the following?  A.decrease the vapor pressure  B.decrease the evaporation rate  C.increase the surface tension  D.increase the viscosity  E.all of the above Answer Key: E Question 7 of 12 4.0/ 4.0 Points Liquids that have high vapor pressure and low boiling points are called  A.abnormal liquids.  B.non-volatile liquids.  C.viscous liquids.  D.volatile liquids.  E.none of the above Answer Key: D Question 8 of 12 4.0/ 4.0 Points Silicon is which type of solid?  A.nonbonding atomic solid  B.metallic atomic solid  C.ionic solid  D.covalent atomic solid  E.molecular solid Answer Key: D Question 9 of 12 4.0/ 4.0 Points In northern climates, it is common to have a layer of frost form on cars that have been out overnight in the winter. During the day the frost layer disappears despite its temperature remaining below freezing. How?  A.The frost evaporates due to the sun heating the solid.  B.The frost cycles as does the saturation level of moisture in the winter air does from night to day.  C.The frost melts due to the sun heating the surface of the car above the melting point.  D.The frost sublimes directly from solid ice to water vapor.  E.none of the above Answer Key: D Question 10 of 12 4.0/ 4.0 Points Which molecule below has hydrogen bonding?  A.CH3OH  B.H2O  C.HF  D.N H3  E.all of the above Answer Key: E

Part 3 of 3 - 0.0/ 10.0 Points Question 11 of 12 0.0/ 5.0 Points Define Pressure. Pressure can be defined as force acting per unit area . Pressure =Force / Area  So here from the formula, as we can seem pressure is inversely in relation with the area, so the pressure will be more on a smaller area compared to the pressure on larger area which are subjected to same force.    Question 12 of 12 0.0/ 5.0 Points Consider the following reaction: 2 H2(g) + O2(g) → 2 H2O(l) How many moles of H2O are formed from 2.9L of O2 at a temperature of 325K and a pressure of 0.988atm? From the equation,  PV = nRT P = 0.988 atm V= 2.9 L T= 325 K R=0.0821 So, by plugging in the given values into the equation, we get, 0.988*2.9 = n(0.0821)325 so n = 0.10738 one mole of oxygen forms 2 moles of H2O, so number of moles of H2O formed = 2(0.10738) = 0.21476 Feedback: Applying gas laws is in Ch 11