Practice: If the barometer in a laboratory reads 34.2 inHg what is the pressure in bars? (1 in = 2.54 cm)

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Standard Temperature and Pressure | 19 mins | 0 completed | Learn |

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Concept #1: Pressure vs. Force

**Transcript**

Welcome back guys. In this new video we're going to take a look at pressure, exactly what is pressure and what causes pressure. So, we're going to say that pressure is just defined as the force exerted per unit of a surface area, on the right side we have a container, inside of this container is we have these black balls, we're going to say these black balls represent individual gas particles and we're going to say that from these black balls we have arrows pointing in different directions, those arrows are basically showing us the direction that the gas particles are taking, gases move in a linear fashion, they move in a straight line and so they're going to be moving in this container bouncing everywhere, bouncing off one another and bouncing off the walls of the container, the pressure that the container has the total pressure inside is the result of each of these gas particles hitting the walls of the container, that's what it is, pressure equals the force the impact that these gas particles are doing on the walls inside of the container, that's all pressure is. So, we're going to say pressure is the force of collisions, the force of each one of these gas particles, hitting the walls of the container adding them up and dividing it by the total area inside of the container, that's what pressure really is, and we're going to say here that the SI unit for pressure, when we talk about pressure, is the Pascal, and we're going to say the units for the Pascal are newtons over meters squared. Now, we're going to say the SI unit of force is the Newton. So, this capital n that we talked about just a second ago, and we're going to say the units for the Newton are kilograms times meters over seconds squared. So, just remember those two SI units, that can easily be a theory question as your professor asks you.

Concept #2: The different units for Pressure

**Transcript**

Despite the fact that the SI unit for pressure is Pascal, chemist all around the world continue to use different units for pressure, because they're just accustomed to it. The Pascal is the SI unit for pressure, but most of the time, you'll see in your books and in different types of research journals from chemists and scientists, they instead like to use atmospheres, torrs or millimeters of mercury. Sometimes you might see bars as well. The Pascal is the SI unit but they tend to like to use these other types of units for pressure.

Now, here we have the different names for pressure. All of these are just different types of pressure, basically different units for it. They're all saying the same thing. An atmosphere is a unit of pressure just like a torr is, just like a bar is, just like kilopascal is. It's going to be important that you know how to convert from one to the other.

It's a long list, but the ones that professor usually focus on the most are: atmospheres, millimeters of mercury, torrs and bars. Those are usually the ones that we see the most, and, of course, Pascals.

Just realize all of them are equal to one another, so we can say that 760 torrs are equal to 1.01325 bars. You could say that one atmosphere is equal to this many Pascals. All these units are in agreement with one another. They all equal one another. We're going to say that one atmosphere equals 760 millimeters of mercury or 760 torrs.

What I also want you to see is that just look at these two right here, the millimeters of mercury and the torrs, they both have the same number, so 760 millimeters of mercury equals 760 torrs. What this really means is that for every one millimeter -- what this means is for every one millimeter of mercury, we have one torr. They're basically the same units.

Just remember that what the SI units for pressure are, what are the SI units for force, what is pressure defined as and then the connections between the different units for pressure because when it comes to gases, we have to remember this because pressure plays a very large role in the property that a gas has.

Although the SI unit for pressure is the **Pascal**, most professors use **atm**, **mmHg** or **torrs** as the everyday units for pressure.

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Example #1: A geochemist heats a limestone (CaCO_{3}) sample and collects the CO_{2} released in an evacuated flask. The CO_{2} pressure is 283.7 mmHg. Calculate the CO_{2} pressure in torrs and atmospheres.

The conversion of units of pressure is simply a **dimensional analysis** question. Recall the dimensional analysis relationships been volume and length.

Practice: If the barometer in a laboratory reads 34.2 inHg what is the pressure in bars? (1 in = 2.54 cm)

0 of 4 completed

Which of the following indicates the greatest pressure?
a. 1 atm
b. 777 torr
c. 5.5 mm Hg
d. 1000 Pa
e. 12 psi

The pressure in Denver. Colorado (elevation 5280 ft). averages about 24.9 in mmHg. Convert this pressure to
a. atm

The pressure on top of Mt. Everest averages about 235 mmHg. Convert this pressure to
a. torr

The world record for lowest pressure (at sea level) was 652.5 mmHg recorded inside Typhoon Tip on October 12,1979, in the Western Pacifie Ocean. Convert this pressure to
a. torr

The pressure in Denver. Colorado (elevation 5280 ft). averages about 24.9 in Hg. Convert this pressure to
b. mmHg

The pressure in Denver. Colorado (elevation 5280 ft). averages about 24.9 in Hg. Convert this pressure to
c. psi

Which of the following is NOT a unit for pressure?
A) Pa
B) mmHg
C) atm
D) torr
E) liter

The pressure in Denver. Colorado (elevation 5280 ft). averages about 24.9 in Hg. Convert this pressure to
d. Pa

The pressure on top of Mt. Everest averages about 235 mmHg. Convert this pressure to
b. psi

The pressure on top of Mt. Everest averages about 235 mmHg. Convert this pressure to
c. in Hg

The pressure on top of Mt. Everest averages about 235 mmHg. Convert this pressure to
d. atm

The world record for lowest pressure (at sea level) was 652.5 mmHg recorded inside Typhoon Tip on October 12,1979, in the Western Pacifie Ocean. Convert this pressure to
b. atm

The world record for lowest pressure (at sea level) was 652.5 mmHg recorded inside Typhoon Tip on October 12,1979, in the Western Pacifie Ocean. Convert this pressure to
c. in Hg

The world record for lowest pressure (at sea level) was 652.5 mmHg recorded inside Typhoon Tip on October 12,1979, in the Western Pacifie Ocean. Convert this pressure to
d. psi

Mars has an average atmospheric pressure of 0.007 atm.Would it be easier or harder to drink from a straw on Mars than on Earth?

Convert 1.50 atm to torr.
A) 760 torr
B) 875 torr
C) 1140 torr
D) 1000 torr
E) 1520 torr

The pressure on top of Mt. Everest averages about 235 mmHg.1.) Convert this pressure to torr.2.) Convert this pressure to psi.3.) Convert this pressure to inHg.4.) Convert this pressure to atm.

Convert 1.50 atm to torr.
A) 760 torr
B) 875 torr
C) 1140 torr
D) 1000 torr
E) 1520 torr

A gauge on a compressed gas cylinder reads 2200 psi (pounds per square inch; 1 atm = 14.7 psi). Express this pressure in each of the following units.b. megapascals (MPa)

Canadian tire pressure gauges are marked in units of kilopascals. What reading on such a gauge corresponds to 32 psi?

Convert the following:(b) 992 torr to bar

The pressure of the atmosphere on the surface of the planet Venus is about 88.8 atm. Compare that pressure in psi to the normal pressure on earth at sea level in psi

Convert the following:(a) 0.745 atm to mmHg

Freon-12 (CF2Cl2) is commonly used as the refrigerant in central home air conditioners. The system is initially charged to a pressure of 4.8 atm. Express this pressure in each of the following units (1 atm = 14.7 psi).b. torr

Consider this scenario and answer the following questions: On a mid-August day in the northeastern United States, the following information appeared in the local newspaper: atmospheric pressure at sea level 29.97 in. Hg, 1013.9 mbar.(b) The pressure near the seacoast in the northeastern United States is usually reported near 30.0 in. Hg. During a hurricane, the pressure may fall to near 28.0 in. Hg. Calculate the drop in pressure in torr

Why are sharp knives more effective than dull knives (Hint: think about the definition of pressure)?

A typical barometric pressure in Kansas City is 740 torr. What is this pressure in atmospheres, in millimeters of mercury, and in kilopascals?

A medical laboratory catalog describes the pressure in a cylinder of a gas as 14.82 MPa. What is the pressure of this gas in atmospheres and torr?

Which units are appropriate
for expressing atmospheric pressures?

Hurricane Wilma of 2005 is the most intense hurricane on record in the Atlantic basin, with a low-pressure reading of 882 mbar (millibars).Convert this reading into torr.

Convert a pressure of 753 torr to a pressure inatm

Hurricane Wilma of 2005 is the most intense hurricane on record in the Atlantic basin, with a low-pressure reading of 882 mbar (millibars).Convert this reading into atmospheres.

Hurricane Wilma of 2005 is the most intense hurricane on record in the Atlantic basin, with a low-pressure reading of 882 mbar (millibars).Convert this reading into inches of Hg.

The pressure of a gas results from a. gas particles colliding with each other. b. gas particles colliding with the container walls. c. the sum of the volumes of the particles being larger than the container volume.

Because He gas is pumped into a rigid container at constant temperature, the pressure inside the container increases. Which of the following are true?A. As the pressure increases, there are less collisions of helium atoms with the wall of the container B. As the pressure increases, the volume of container also increases C. More than one D. More collisions between helium atoms and the wall of the container will occur as the pressure inside the container increases. E. None of the above

Rank these gas samples according to pressure.

An ordinary gasoline can measuring 30.0 cm by 25.0 cm by 20.0 cm is evacuated with a vacuum pump.Assuming that virtually all of the air can be removed from inside the can, and that atmospheric pressure is 14.7 psi, what is the total force (in pounds) on the surface of the can?

What is 2.3 atm in kPa?A. 333 B. 305 C. 155 D. 233 E. 213

The atmospheric pressure is 700 mm Hg. What is the pressure in inches of Hg?A) 16.0 in HgB) 0.921 in HgC) 13.5 in HgD) 27.6 in HgE) 32.5 in Hg

The North American record for highest recorded barometric pressure is 31.85 inHg, set in 1989 in Northway, Alaska.Convert this pressure to kPa (kilopascals).

In the United States, barometric pressures are generally reported
in inches of mercury (in. ). On a beautiful summer day in Chicago, the barometric pressure is 30.47 in. Hg .Convert this pressure to torr.

Consider a planet where the pressure of the atmosphere at sea
level is 2500 mmHg. Will water behave in a way that can sustain
life on this planet?

Perform the following conversions of pressure.2.50 atm to bars

Convert each of the pressures described below to atm:(a) At the peak of Mt. Everest, atmospheric pressure is only 2.75×10 2 mmHg.

A typical barometric pressure in Denver, Colorado, is 615 mm Hg. What is this pressure in atmospheres and kilopascals?

A typical barometric pressure in Redding, California, is about 750 mm Hg. Calculate this pressure in atm and kPa.

An oxygen tank contains oxygen (O2) at a pressure of 9 50 atm. Part AWhat is the pressure in the tank in torr? Part BWhat is the pressure in the tank in mmHg?

The pressure 70.0 meters under water is 788 kPa.What is this pressure in atm?What is this pressure in mmHg?

High-pressure liquid chromatography (HPLC) is a method used in chemistry and biochemistry to purify chemical substances. The pressures used in this procedure range from around 500 kilopascals (500,000 Pa) to about 60,000 kPa (60,000,000 Pa). It is often convenient to know the pressure in torr. If an HPLC procedure is running at a pressure of 2.90 x 10 8 Pa, what is its running pressure in torr? Express the pressure numerically in torr.

The atmospheric pressure in New York City on a certain day was 768 mm Hg. What was the pressure in kPa?a. 1.02 x 105 kPa b. 584 kPa c. 5.76 x 10-3 kPa d. 102 kPa e. none of the above

The pressure in car tires is often measured in pounds per square inch (lb/in.2), with the recommended pressure being in the range of 25 to 45 lb/in.2. Suppose a tire has a pressure of 37.5 lb/in.2. Convert 37.5 lb/in.2 to its equivalent in atmospheres. Express the pressure numerically in atmospheres.

The pressure 70.0 meters under water is 788 kPa. What is this pressure in bar? What is this pressure in torr?

On a climb up Mt. Whitney, the atmospheric pressure is 531 mmHg.Part A What is the pressure in atm? Part B What is the pressure in torr?

An airplane cabin is pressurized to 620 mmHg. What is the pressure inside the cabin in atmospheres?

The atmospheric pressure on the surface of Venus is 9120. kPa. Calculate the atmospheric pressure in atm. Be sure your answer has the right number of significant digits.

The density of mercury is 13.5 g/mL and the density of water is 1.00 g/mL. lf a mercury barometer reads 727 mmHg, what is the barometric pressure in cm H 2O?

An ordinary gasoline can measuring 30.0 cm by 15.0 cm by 10.0 cm is evacuated with a vacuum pump. Assuming that virtually all of the air can be removed from inside the can, and that atmospheric pressure is 14.7 psi, what is the total force (in pounds) on the surface of the can?

The typical atmospheric pressure on top of Mt. Everest (29,028 ft) is about 265 torr. Convert this pressure to the following units.pascals

Rank the common units of pressure in order of smallest to largest unit.

The gravitational force exerted by an object is given by F = mg, where F is the force in newtons, m is the mass in kilograms, and g is the acceleration due to gravity (9.81 m/s 2). (a) Use the definition of the pascal to calculate the mass (in kg) of the atmosphere above 1 m2 of ocean. (1 Pa = 1.01325x105 N/m2)

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