Practice Test 2 - Reagent Preparation Flashcards
A lab technician is making a solution by combining 3 parts of a solute with 7 parts of water. How many millilitres of the solute and water are needed to make 100 mL of the solution?
a) 7 mL of solute and 3 mL of water
b) 10 mL of solute and 70 mL of water
c) 30 mL of solute and 70 mL of water
d) 70 mL of solute and 30 mL of water
c) 30 mL of solute and 70 mL of water
3 + 7 is a total of 10 parts.
Therefore, the amount of solution needed:
100 mL x 3/10 = 30 mL
Amount of water needed:
100 mL x 7/10 = 70 mL
If a dilution ratio of 7:10 is used to make an acetic acid solutin and the final volume of the solution 950 mL, then what is the volume of the solute?
a) 58 mL
b) 101 mL
c) 391 mL
d) 559 mL
c) 391 mL
A dilution ratio of 7:10 means the solution contains 7 parts solute and 10 parts solvent, making 17 parts in total. In other words, 7/17ths of the solution is solute.
To find the volume of solute in a solution, multiply the volume of the solution that is solute:
950 mL x 7/17 - 391 mL of solute
What is one part chemical to five parts water expressed as a dilution factor?
a) 3
b) 4
c) 5
d) 6
d) 6
A dilution factor of 6 means thee total volume of the solution is 6 times higher than the volume of the solute.
To make a dilution with a dilution factor of 6, you would mix 1 part chemical with 5 parts water, giving the total of 1 part chemical to 6 parts solution.
How many millilitres of an 80% acetic acid solution is needed to make 2 litres of a 10% acetic acid solution?
a) 20 mL
b) 50 mL
c) 100 mL
d) 250 mL
d) 250 mL
The dilution formula is:
c1 x v1 = c2 x v2
where:
c1 is the initial concentration
v1 is the initial volume
c2 is the final concentration
v2 is the final volume
Using the dilution formula:
c1 x v1 = c2 x v2
80 x v1 = 2000 x 10
80 x v1 = 20,000
v1 = 20,000/80
v1 = 250 mL
If glassware needs to be dried and used immediately after washing, you should rinse it with:
a) acetic acid
b) acetone
c) hydrogen peroxide
d) sodium nitrate
b) acetone
Adding acetone to wet glassware lowers the surface tension of the water and helps the water to evaporate quickly.
The proper time for sterilizing an article in the autoclave:
a) is approximately 10 too 15 minutes
b) is approximately 15 to 20 minutes
c) depends on the type of indicator being used
d) depends no what is being autoclaved
d) depends no what is being autoclaved
What type of water does an autoclave use?
a) Distilled water
b) Mineral water
c) Salt water
d) Tap water
a) Distilled water
Autoclaves require the cleanest water possible to function properly, such as distilled water or deionized water.
What type of glass is autoclavable?
a) Borosilicate
b) Float
c) Lead
d) Soda-lime
a) Borosilicate
Borosilicate glass has a high resistance to temperature change, making it suitable for autoclaving. For this reason, borosilicate glass is commonly used in laboratory equipment, such as beakers, flasks, and test tubes, which are often sterilized in autoclaves.
Lead glass is not considered to be autoclavable. This is because lead glass is highly susceptible to thermal shock and can easily break or crack under the high temperatures and pressure used in autoclave sterilization.
Soda-lime glass, also known as float glass, is not highly resistant to thermal shock and is therefore not recommended for use in autoclaves.
Which pH buffer solution is typically used first when calibrating a pH meter?
a) pH 1
b) pH 4
c) pH 7
d) pH 10
c) pH 7
When calibrating a pH meter, a buffer of pH 7 is typically uused first, followed by a buffer of either pH 4 or pH 10.
