Combined Gas law

Homework Due May 11


Solve the following problems 73 - 92

STP means Standard Temperature and Standard Pressure (1 atm and 273 °K) could be written as Standard Conditions too.
Combined Gas Law 
73. A gas has a volume of 800.0 mL at –23.00 °C and 300.0 torr. What would the volume of the gas be at 227.0 °C and 600.0 torr of pressure?

74. 500.0 liters of a gas are prepared at 700.0 mmHg and 200.0 °C. The gas is placed into a tank under high pressure. When the tank cools to 20.0 °C, the pressure of the gas is 30.0 atm. What is the volume of the gas?

75. What is the final volume of a 400.0 mL gas sample that is subjected to a temperature change from 22.0 °C to 30.0 °C and a pressure change from 760.0 mmHg to 360.0 mmHg?

76. What is the volume of gas at 2.00 atm and 200.0 K if its original volume was 300.0 L at 0.250 atm and 400.0 K.

77. At conditions of 785.0 torr of pressure and 15.0 °C temperature, a gas occupies a volume of 45.5 mL. What will be the volume of the same gas at 745.0 torr and 30.0 °C?

78. A gas occupies a volume of 34.2 mL at a temperature of 15.0 °C and a pressure of 800.0 torr. What will be the volume of this gas at standard conditions?

79. The volume of a gas originally at standard temperature and pressure was recorded as 488.8 mL. What volume would the same gas occupy when subjected to a pressure of 100.0 atm and temperature of -245.0 °C?

80. At a pressure of 780.0 mmHg and 24.2 °C, a certain gas has a volume of 350.0 mL. What will be the volume of this gas under STP

81. A gas sample occupies 3.25 liters at 24.5 °C and 1825 mmHg. Determine the temperature at which the gas will occupy 4250 mL at 1.50 atm.

82. If 10.0 liters of oxygen at STP are heated to 512 °C, what will be the new volume of gas if the pressure is also increased to 1520.0 mm of mercury?

83. What is the volume at STP of 720.0 mL of a gas collected at 20.0 °C and 3.00 atm pressure?

84. 2.00 liters of hydrogen, originally at 25.0 °C and 750.0 mm of mercury, are heated until a volume of 20.0 liters and a pressure of 3.50 atmospheres is reached. What is the new temperature?

85. A gas balloon has a volume of 106.0 liters when the temperature is 45.0 °C and the pressure is 740.0 mm of mercury. What will its volume be at 20.0 °C and 780 .0 mm of mercury pressure?

86. If the absolute temperature of a given quantity of gas is doubled and the pressure tripled, what happens to the volume of the gas?

87. 73.0 mL of nitrogen at STP is heated to 80.0 °C and the volume increase to 4.53 L. What is the new pressure?

88. 500.0 mL of a gas was collected at 20.0 °C and 720.0 mmHg. What is its volume at STP?

89. A sample of gas occupies 50.0 L at 15.0 °C and 640.0 mmHg pressure. What is the volume at STP?

90. A gas is heated from 263.0 K to 298.0 K and the volume is increased from 24.0 liters to 35.0 liters by moving a large piston within a cylinder. If the original pressure was 1.00 atm, what would the final pressure be?

91. The pressure of a gas is reduced from 1200.0 mmHg to 850.0 mmHg as the volume of its container is increased by moving a piston from 85.0 mL to 350.0 mL. What would the final temperature be if the original temperature was 90.0 °C?

92. If a gas is heated from 298.0 K to 398.0 K and the pressure is increased from 2.230 x 103 mmHg to 4.560 x 103 mmHg what final volume would result if the volume is allowed to change from an initial volume of 60.0 liters?

Boyle's Law

Homework Due May 3, 2017

Boyle's Law Worksheet

Boyle's gas law states the volume of a gas is inversely proportional to the pressure of the gas when temperature is held constant. This example problem uses Boyle's law to find the volume of a gas when pressure changes.

Boyle's Law Example Problem

A balloon with a volume of 2.0 L is filled with a gas at 3 atmospheres. If the pressure is reduced to 0.5 atmospheres without a change in temperature, what would be the volume of the balloon?

Solution:
Since the temperature does not change, Boyle's law can be used. Boyle's gas law can be expressed as:
P_iV_i = P_fV_f
Where

P_i = initial pressure
V_i = initial volume
P_f = final pressure
V_f = final volume

To find the final volume, solve the equation for V_f:

V_f = P_iV_i/P_f

V_i = 2.0 L
P_i = 3 atm
P_f = 0.5 atm

V_f = (2.0 L)(3 atm)/(0.5 atm)
V_f = 6 L/0.5
V_f = 12 L

SOLVE THE FOLLOWING PROBLEMS

1.	State the pressure-volume law both in words and in the form of an equation.
2.	To compress nitrogen at 1 atm from 750 mL to 500 mL, what must the new pressure be  if the temperature is kept constant?
3.	If oxygen at 128 kPa is allowed to expand at constant temperature until its pressure is 101.3 kPa, how much larger will the volume become?
4.	A sample of nitrogen at 101.3 kPa with a volume of 100 mL is carefully compressed at constant temperature in successive changes in pressure, equalling 5 kPa at a time, until the final pressure is 133.3 kPa. Calculate     each new volume and prepare a plot of P versus V, showing P on the horizontal axis.
5.	A sample of nitrogen at 20oC was compressed from 300 mL to 0.360 mL and its new pressure was found to be 400.0 Pa. What was the original pressure in kPa?
6.	The pressure on 6.0 L of a gas is 200 kPa. What will be the volume if the pressure is doubled, keeping the temperature constant?
7.	What would be the new volume if the pressure on 600 mL is increased from 90 kPa to 150 kPa?
8.	A student collects 25 mL of gas at 96 kPa. What volume would this gas occupy at 101.325 kPa. There is no change in temperature or mass.
9.	A gas measuring 525 mL is collected at 104.66 kPa. What volume does this gas occupy at 99.33 kPa?
10.	A mass of gas occupies 1 L at 1 atm. At what pressure does this gas occupy
	a) 2 litres,                      b) 0.5 litres
11.	From the data in the following table calculate the missing quantity (assuming constant temperature).
	a)    V1 = 22.4 L;   P1= 1 atm;    P2 = ? atm;   V2 =  2.8 L
	b)    V1 = 60 mL;   P1 = ? kPa;   P2 = 101.3 kPa;  V2 = 16 mL
	c)     V1 = ? m3 ;    P1 = 40 Pa;   P2 = 100 kPa;  V2 = 1.0 L
	d)    V1 = 2.50 L;   P1 = 7.5 atm;   P2 = ? atm;  V2 = 100 mL

Buoyant Forces

Homework Due May 2nd, 2017

Answer the following questions

1)What equation would you use to find the volume of a rectangular box?

A) volume = length × width × height B) volume = length + width + height C) volume =

length × width D) volume = length + width

2)Which of the following is the equation used to calculate a substance’s density?

A) D = V/m B) D = m/V C) D = m + V D) D = V × m

3)What happens to a solid object with a density that is less than the density of water when it is

placed in water?

A) The object dissolves in the water. B) The object displaces a quantity of water greater

than its volume. C) The object settles to the bottom of the water. D) The object floats on

top of the water.

4)Which of the following units are best for expressing the density of a solid?

A) g/mL B) m3/kg C) g/cm3 D) N/cm3

5)Which physical property of matter describes the relationship between mass and volume?

A) density B) ductility C) reactivity D) weight

6)Why does ice float on top of liquid water?

A) Ice has a lower density than water. B) Ice has a higher density than water. C) Ice is a

solid. D) Ice is colder than water.

7)If you have 5 mL of a liquid that has a mass 20 g, what is the density of the liquid?

A) 0.79 mL/g B) 0.79 g/mL C) 1.26 mL/g D) 4 g/mL

8)To compare the densities of oil and water, pour the liquids into a container and observe how

they

A) change color. B) evaporate quickly. C) separate into layers. D) create an odor.

9)What units would you use to measure liquid volume in an experiment?

A) grams or kilograms B) meters or centimeters C) newtons D) liters or milliliters

10) Why is density considered a useful property for identifying matter?

A) Different substances have the same densities. B) Density is unique to each substance.

C) Density predicts whether objects float. D) Density varies at different temperature.

11)What property of matter is demonstrated by the fact that you cannot fit any more books onto a

bookshelf that is already filled?

A) inertia B) mass C) volume D) weight

13)Why doesn’t an ice cube float in air?

A) Water is less dense than air. B) Air is denser than ice. C) An ice cube is denser than

air. D) Air has more pressure.

14)Which of the following is NOT true about water?

A) Water is more dense than air. B) A volume of water weighs more than the same

volume of air. C) Water exerts more pressure than air. D) Water is less dense than air.

15)What is the secret of how a ship floats?

A) the number of passengers it carries B) the amount of cargo it carries C) its hollow

shape D) its size

16)Which of the following causes an object to buoy up?

A) buoyant force greater than the object’s weight B) buoyant force less than the object’s

weight C) buoyant force equal to the object’s weight D) high air pressure

17)How do you find the volume of an irregular solid?

A) by multiplying the lengths of its sides B) through water displacement C) by using a

balance D) by weighing it

19)Which of the following substances is less dense than air?

A) water B) helium C) ice D) gold

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20) Why do air bubbles in water rise to the surface?

 A) Liquids cannot be compressed very much. B) Water is about 1,000 times denser than

air. C) Pressure is the amount of force exerted on a given area. D) The weight of the

atmosphere pushes down on the water.

21) Snowshoes enable a person to walk on deep snow because the snowshoes

A) decrease the person’s weight on the snow. B) increase the area over which the

person’s weight is distributed. C) increase the pressure on the snow. D) increase the

buoyancy of the person.

22) A unit of pressure is called a

A) bernoulli. B) pascal. C) pound. D) meter.

23) Given that the air pressure outside your body is so great, why aren’t you crushed?

A) Human skin is extremely strong. B) Earth’s gravity cancels out the air pressure.

C) Pressure inside your body balances the air pressure outside your body. D) Inertia

changes the pressure before it comes into contact with you.

24) Air pressure decreases as

A) velocity increases. B) elevation increases. C) acceleration decreases. D) gravity

increases.

25) Water pressure increases as

A) depth increases. B) gravity increases. C) force decreases. D) acceleration decreases.

 26) Which of the following is true of the buoyant force?

A) It acts in the downward direction. B) It acts with the force of gravity. C) It acts in the

upward direction. D) It makes an object feel heavier.

 27) What effect does a buoyant force have on a submerged object?

A) It causes the object to sink in a fluid. B) It causes a net force acting upward on the

object. C) It causes the object to float in a fluid. D) It causes a net force acting

downward on the object.

28)According to Archimedes’ principle, if an object floats, the volume of displaced water is

equal to the volume of

A) the entire object. B) the portion of the object that is above water. C) the portion of

the object that is submerged. D) exactly half of the object.

29) What scientific rule states that the buoyant force on an object is equal to the weight of the

fluid displaced by the object?

A) Archimedes’ principle B) Pascal’s principle C) Bernoulli’s principle D) Newton’s

third law of motion

30) A ship stays afloat as long as the buoyant force is

A) less than the ship’s weight. B) greater than the ship’s weight. C) less than the ship’s

speed. D) greater than the ship’s speed.

31) The mass per unit volume of a substance is its

A) density. B) buoyancy. C) weight. D) fluid pressure.

 32) Which of these substances is the LEAST dense?

A) wood B) copper C) mercury D) rubber

 33) Pressure can be measured in units of

A) newtons. B) newtons per square centimeter. C) newtons per centimeter. D) newtons

per cubic centimeter.

  35) Fluid pressure is the total force exerted by the fluid divided by

A) the area over which the force is exerted. B) the acceleration of the force. C) the

gravitational pull within the fluid. D) water pressure or depth.