Concentration and Exposure Ans

1. The label CORROSIVE on a chemical container indicates
Ans : ( b ) that contact destroys living tissue as well as equipment

2. FLAMMABLE means
Ans : ( a ) easily ignited and capable of burning rapidly

3. " Fatal if swallowed " indicates
Ans : ( c ) that the substance will cause death if ingested

4. What is the correct way to handle the following situation? Briefly explain.

a. Chemical : Acetic asid
i. Inhalation exposure
Ans : Remove the person from the exposure. Begin rescue breathing ( using universal precautions ) if breathing has stopped and CPR if heart action has stopped. Transfer promptly to medical facility. Medical observation is recommended for 24 to 48 hours after breathing overexposure, as pulmonary edema may be delayed.

ii. Dermal exposure
Ans : Quickly remove contaminated clothing. Immediately wash contaminated skin with large amounts of soap and water. Seek medical attention immediately.

iii. Eye exposure
Ans : Immediately flush with large amounts of cool water. Continue for at least 30 minutes, occasionally lifting upper and lower lids. Remove contact lenses, if worn, while rinsing. Immediate medical attention is necessary.

b. Chemical : Etanol
i. Oral exposure
Ans : Intoxicating if ingested. (If ingested in undiluted form, it has a severe drying effect on mucous membranes of mouth and throat.) NEVER MAKE AN UNCONSCIOUS PERSON VOMIT OR DRINK FLUIDS. Wash out mouth thoroughly, and give plenty of water to drink. Do not induce vomiting. Get medical attention immediately.

ii. Inhalation exposure
Ans : Occupational exposure limits (8-hour reference period) 1000 ppm (1900 mg/m³). Intoxicating if continuously inhaled for a long period of time. Move the person to fresh air, immediately perform artificial respiration if breathing has stopped. When breathing is difficult, properly-trained personnel may administer oxygen. Keep the person warm and at rest. Get medical attention promptly.

iii. Eye exposure
Ans : Prior to exposure it irritates the eyes and can be damaging if large amount is splashed into eyes. Wash eyes promptly with plenty of water, while lifting the eye lids. Continue to rinse for at least 15 minutes, and get medical attention.

5. Explain on how to prepare 30ml of 0.95% ( w/v ) NaCl
Ans :

Given that units of “%(w/v)” which is the percent weight/volume gives the weight of substance relative to the volume of solution, where 1%(w/v) / 1 g/100 ml. Thus, given a final concentration of a chemical assuming it is started with a pure, dry substance and the required final volume, gram of the chemical is such that the final volume (ml) x fractional weight.
Hence to prepare a 30 ml of 0.95% NaCl: 30 x 0.0095 = 0.285g of NaCl is required. This would be prepared by dissolving 0.285g of NaCl in approximately 20ml of water, and then bring the final volume up to 30ml in a graduated cylinder.
6. A researcher wants to make to make 500mL of 0.050 M HCl by diluting a 6.0 M HCl solution. How much of that solution should be used?
Ans :

The calculations performed under an equation whereas the molarity of the concentrated solution times the volume of the concentrated solution is equal to the molarity of the dilute solution times the volume of the dilute solution.
(Mcon) (Vcon) = (Mdil) (Vdil)

(Vcon) =

(Mdil) (Vdil) ÷ (Mcon)

(Vcon) = [(0.050 M)(500mL)] ÷ (6.0 M)

Vcon = 4.2 mL

7. An experiment requires 800mL of 5.0% (w/v) MgSO4. How would you prepare the solution?
Ans :

5g of MgSO4 solute with 100ml of solvent= 5% (w/v) solution

X /800ml = 5g/100ml
100X= 4000g
X= 40g

Hence, 800ml of solvent should be added with 40g of solute MgSO4 to produce a 5% (w/v) solution.

8. Does the addition of the solvent change the molarity of a solution when a solution is diluted? Explain .

Ans : Molarity (M) is defined as the number of moles of solute (n) divided by the volume (V) of the solution in liters. It is important to note that the molarity is defined as moles of solute per liter of solution. When the solution is diluted, the solvent has been increased in volume so that it became diluted, this will not change the amount of solute in the solution but it affects the concentration of solute in the solution and this will also change the molarity due to the increase in volume of the solution.