THEA 1100 Lecture Notes - Lecture 2: Hearing Loss, Benzene, Occupational Safety And Health

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redwolf334

4 Oct 2014

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It is the same chemical reaction as iron rusting. It is the breaking down of material as oxidization: oxidization generates heat. An explosion is a really fast fire: all burning materials must be combustible enough to give off vapours, you must have a fire starter to get charcoal to burn. It is the combustible vapours that burn: you must have oxygen in order to have a fire. O2 oxygen: there is no time in life where you should panic. Heat: baking soda is a great for fire, you can cool the fire, smother it, or removing the fuel to put out the fire, dynamite takes away the oxygen. It should be used to put out a fire: there are several classes for fire extinguishers, class a: ordinary heat. You cool a class a fire with water: class b: oil or spirits- fats gasoline paints grease etc.

Related Questions

When a flammable liquid (e.g., gasoline) ignites, the substance actually burning is vapor generated from the liquid. If the concentration of the vapor in the air above the liquid exceeds a certain level (the lower flammability limit), the vapor will ignite if it is exposed to a spark or another ignition source. Once ignited, the heat released is likely to cause additional vaporization of the liquid, and the resulting fire may continue until all combustible material has been consumed.

(a) The flash point is defined as the minimum temperature at which a flammable liquid or volatile solid gives off sufficient vapor to form an ignitable mixture with air near the surface of the liquid or within a vessel (page 2-515, Perryâs Chemical Engineersâ Handbook, see Footnote 1). For example, the flash point of n-octane at 1.0 atm is 13Â°C (55Â°F), which means that dropping a match into an open container of octane is likely to start a fire in a laboratory, but not outside on a cold winter day. (Do not try it! One referenceâL. Bretherick, Bretherickâs Handbook of Reactive Chemical Hazards, 4th Edition, Butterworths, London, 1990, p. 1596âpoints out there is âusually a fair [our emphasis] correlation between flash point and probability of involvement in fire.â)

Suppose you are keeping two solvents in your laboratory, one with a flash point of 15Â°C and the other with a flash point of 75Â°C. How do these solvents differ from the standpoint of safety? What differences, if any, should there be in how you treat them?

(b) The lower flammability limit (LFL) of methanol in air is 6.0 mole%. Calculate the temperature at which a saturated methanolâair mixture at 1 atm would have a composition corresponding to the LFL. What is the relationship of this value to the flash point, and what value would you assign the flash point of methanol?

(c) Give reasons why it would be unsafe to maintain an open container of methanol in an environment below the LFL (i.e., the value calculated in Part (b)) if there are ignition sources nearby. List common ignition sources that may be found in a laboratory.

Can someone please paraphrase this to me in short sentences...

1. Obtain a benzoic acid pellet, determine the mass of the pellet on the analytical balance and record the mass in your hard covered note book. The error for the analytical balance is ï± 0.0005 g. Attach approximately 10.0 cm of fuse wire as shown by your Instructor (use the length of the card that holds the fuse wire, the card is already calibrated in heat units, cal or 4.18 J units) and adjust it to give firm contact with the benzoic acid pellet. Avoid kinks in the fuse wire.

2. Carefully assemble the bomb, keeping surfaces of closure scrupulously clean. Dismantled parts should be placed on a clean, dry paper towel. Place the bomb on the bench next to the O2 cylinder. Tighten cover by hand. The Instructor must assist you in connecting the bomb to the O2 cylinder, and slowly admit oxygen to a final pressure of 20 atm (280 psi.) Close valves on cylinder. Relieve pressure in line by means of the black knob on the regulator. Remove the gas coupling and check the circuit again.

3. Place the bomb in the calorimeter and make sure the ignition wires are connected properly. Carefully fill the inner reservoir in the calorimeter with 2000 mL distilled water, using the volumetric flask provided. The water should completely cover the bomb; no oxygen bubbles should escape from the bomb if the seal is good. If there is a substantial leak, the bomb should be dried and refilled with oxygen. Small leaks are insignificant.

4. Connect the motor and pulley experiment with the o-ring provided and starts the stirrer. Connect the leads on the outside of the bomb jacket to the 10 cm fuse in the igniter

. 5. Turn on the stirrer. For this, data points should be collected every ten seconds up to a total of 150 data points.

6. After at least 12 data points have been collected, and the temperature is reasonably constant or shows only a small up- or downward trend, press and hold the ignition button on the ignitor for approximately 1second. You will see the red light on the ignition box flash on and off again, showing that the fuse wire has burned. You should NOT be standing over the bomb while igniting the bomb!! Stand back from the bomb for at least 15 seconds. If combustion has occurred, the temperature will start to rise within the next two or three data points.

7. Keep recording data until the 150 points finishes.

8. Remove the bomb from the calorimeter and relieve the pressure by opening the valve. BE SURE to open the release valve before trying to unscrew the top of the bomb! 9. Measure the remaining length of unoxidized fuse wire. (This information is needed to correct for its heat of combustion). Carefully clean and dry the calorimeter and sample pan.

10. Repeat this procedure with the second benzoic acid pellet.

11. Once you have good data for benzoic acid, allowing you to calculate the calorimeter constant C, repeat the full procedure for each of the two sucrose samples.

Hi, I am not well at all, and need to submit this lab as soon as possible and am busy with alot of other stuff too. Please help with it. Will be really thankful and would rate good.

Introduction

Decomposition of Sodium Chlorate Mass, Moles, and the Chemical Equation

Sodium chlorate is used as a source of oxygen in emergency oxygen generators. So- called oxygen canisters or oxygen candles are found on airplanes, submarines, even the space station â anywhere oxygen might be in short supply in case of an emergency. Sodium chlorate decomposes upon heating or in the presence of metals to give oxygen gas. What is the chemical equation for the decomposition of sodium chlorate?

Concepts

ï· Moles ï· Balanced chemical equation

ï· Molecular formula ï· Stoichiometry

Background

Sodium chlorate, NaClO₃, is a colorless, odorless, white solid that melts at 248 Â°C. When heated above 300 Â°C, it begins to lose oxygen. The ultimate products of the thermal decomposition of sodium chlorate are oxygen gas and a white solid. Based on the molecular formula of sodium chlorate, three possible reactions will account for the loss of oxygen gas upon heating (Equations 1-3). Note that equations 1-3 are not balanced.

Equation 1 2NaClO₃(s) â 2NaClO₂(s) + O₂(g)

Equation 2 NaClO₃(s) â NaClO(s) + O₂(g)

Equation 3 2NaClO₃(s) â 2NaCl(s) + 3O₂(g)

What is the actual chemical equation for the thermal decomposition of sodium chlorate? All of the possible sodium-containing products n Equations 1-2 are real compounds: sodium chlorite, NaClO₂; sodium hypochlorite, NaClO; and sodium chloride, NaCl. All are white solids at room temperature. It is possible to determine the chemical equation for the decomposition of sodium chlorate by applying the principles of stoichiometry to the masses of the reactants and products.

Safety Precautions:

Sodium chlorate is a strong oxidizing agent and a dangerous fire risk; it is slightly toxic by ingestion. Contact with metal powders or combustible organic compounds may cause fires. Keep away from contact with organic materials, including rubber stoppers, rubber tubing, etc. Avoid contact with eyes and skin. Do NOT dispose of exess sodium chlorate in the trash.

When heating sodium chlorate, use only a small amount of solid (0.25-0.40 g) in a Pyrex test tube. Inspect the test tube for chips and cracks before use and handle the test tube using a test tube clamp. Distribute the solid evenly along the bottom of the test tube and heat the test tube clamp. If any smoke is produced, remove the test tube from the flame until the reaction subsides. Do not inhale the smoke. Allow the test tube to cool completely on a wire gauze with a ceramic, heat-resistant center. Wear chemical splash goggles and chemical-resistant gloves and apron.

Procedure:

Measure all masses to the nearest 0.01 g and record all data in the data table.

Obtain two medium test tubes. Label them 1 and 2.

Measure and record the mass of each test tube.

Using a spatula, add approximately 0.2-0.4 g of sodium chlorate to the bottom of each test tube.

Measure and record the combined mass of each test tube and sodium chlorate.

Place test tube #1 in a test tube clamp. Holding the test tube in an almost horizontal position, gently tap the test tube to distribute the solid sodium chlorate evenly along the bottom one-third of the test tube.

Light a Bunsen burner.

Holding test tube #1 with the test tube clamp, slowly move the test tube back and forth through the burner flame to gently heat the solid. The solid should begin to melt and bubble slightly. Caution: Do not aim the opening of the test tube at anymore.

Quickly remove the test tube from the flame if a white smoke is given off from the open end of the test tube. The smoke represents a loss of starting material due to evaporation of molten sodium chlorate and will reduce the yield of product. A small amount of smoke may be inevitable and should not interfere with the accuracy of the results.

Continue to heat the test tube in the burner flame until no more bubbling is observed and the material in the test tube has solidified.

Allow the test tube to cool completely on a wire gauze with a ceramic center.

While test tube #1 is cooling, repeat steps 5-11 sing test tube #2.

When test tube #1 has cooled to room temperature, measure the combined mass of the test tube and its solid contents.

Reheat test tube #1 gently for an additional three minutes.

Cool the test tube on the wire gauze until it is room temperature. Measure the mass a second time. If the second mass differs from the first mass by more than 0.02 g, repeat the heating cycle a third time.

Repeat steps 13-15 using test tube #2.

Data Table:

Trial 1

Weight of beaker --- 68.1887g

Weight of test tube -- 19.3538g

Weight of NACLO3 -- 0.3341g

Everything together -- 87.9155g

1st time burning:-- 87.8851g

2nd time burning:-- 87.7630g

3rd time burning:-- 87.7626g

Trial 2

Weight of beaker --- 68.1886g

Weight of test tube -- 22.8518g

Weight of NACLO3 -- 0.3154g

Everything together -- 91.3508g

1st time burning:-- 91.2078g

2nd time burning:-- 91.2103g

Post-Lab Calculations and Analysis:

1) For each trial, find the initial mass of sodium chlorate and calculate the number of moles of sodium chlorate.

2) Based on the molar masses of the three possible solid products in Equations 1-3, and the number of moles of reactant in each case, calculate the expected masses of the three possible products for Trials 1 and 2.

3) Compare the actual mass of product obtained in Trials 1 and 2 with the calculated or expected masses. What is the balanced chemical equation for the decomposition of sodium chlorate? Explain.

4) Use the following equation to determine the percent error in the mass of solid obtained.

â (actual mass â expected mass) / expected mass

5) Consider the following potential sources of error in this experiment. Explain whether they would have caused the actual mass of solid product to be lower or higher than the expected value.

a)The sodium chlorate did not decompose completely.

b)The sodium chlorate was heated too fast, allowing considerable white smoke to escape from the test tube.

c)The sodium chlorate absorbed some moisture from the air before the experiment began and was not completely dry.

THEA 1100 Lecture Notes - Lecture 2: Hearing Loss, Benzene, Occupational Safety And Health

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