Chapter 9: Laboratory Procedures

What is its most likely temperature in degrees Celsius if a liquid is just a little cooler than room temperature (70F)?

20C

How many grams of dry sodium bicarbonate (baking soda) must you add to 1.5 liters of water to make a 250 milligram per liter solution? a. .375 g b. .250g c. .175g d. .500g

a. .375g

Given the following measurements calculate the total suspended solids in milligrams per liter. -weight of crucible + clean filter = 19.0768g -weight of crucible + filter + solids after drying = 19.0899g -volume of sample filtered = 122 mL a. 107mg/L b. 13.1 mg/L c. 925 mg/L d. 7.6 mg/L

a. 107mg/L

What is the normality of a 1.5 M solution of H₂SO₄ (sulfuric acid)? a. 3 N b. 2 N c. 1.5 N d. .75 N

a. 3 N

Which statement is true about two acid solutions of equal normality (1.0 N) if one solution was made from hydrochloric acid (HCI) and one from sulfuric acid (H₂SO₄)? a. making the solutions required twice as many moles of HCI as H₂SO₄ b. making the solutions required half as many moles of HCI as H₂SO₄ c. the HCI solution is safer to handle because it is less concentrated d. the H₂SO₄ solution is safer to handle because it is less concentrated

a. making the solutions required twice as many moles of HCI as H₂SO₄

Which of the following common practices would be acceptable from a safety standpoint? a. wearing a lab coat over your work clothes b. wearing sandals c. wearing contact lenses without separate eye protection d. eating lunch in a specially designated laboratory location

a. wearing a lab coat over your work clothes

What is the best practice when diluting a strong acid with water?

add baking soda to the strong acid (1:10), then add water to the desired final volume, and mix

If you have 350mL of a 400mg/L solution of aluminum sulfate, how much water would you have to add to bring the concentration down to 100mg/L? Assume that you are adding water that does not contain any aluminum sulfate(C2= 0). a. 70mL b. 1400mL c. 143mL d. 1750mL

b. 1400mL

Given the following measurements, calculate the volatile suspended solids (VSS) concentration in milligrams per liter. -weight of crucible + clean filter = 19.3052 g -weight of crucible + filter + solids after drying = 19.3103 g -weight of crucible + filter + solids after ignition = 19.3086g -volume of sample filtered = 92 milliliters a. 12.2 mg/L b. 18.5 mg/L c. 38.2 mg/L d. 57.3 mg/L

b. 18.5 mg/L

Two waste containers hold different volumes and concentrations of chrome solution. Container A holds 710mL of a 200 microgram per liter (ug/L) chrome solution. Container b holds 460mL of a 350 ug/L chrome solution. If you pour the two volumes together, what is the chrome concentration in the mixture? a. 243 ug/L b. 259 ug/L c. 275 ug/L d. 291 ug/L

b. 259 ug/L

Three of the following tests can be done with a probe-type instrument. Which one is the exception? a. EC b.TSS c. DO d. pH

b. TSS

Which sample will have the highest concentration in a spectrophotometer colorimetric measurement? a. the one with the highest transmittance b. the one with the highest absorbance c. the one with the lightest color d. the one with the highest turbidity

b. the one with the highest absorbance

In January, operator Bob Ross made a standard solution used in a chemical test. Which of the following labels is the best format? a. reagent for the alkalinity test, BR, 1/25/19 b. sodium carbonate (Na₂CO₃), BR, 1/25/19 c. 0.1 N sodium carbonate (Na₂CO₃), BR, 1/25/19 d. Na₂CO₃ standard solution, made 1/25/19

c. 0.1 N sodium carbonate (Na₂CO₃), BR, 1/25/19

How many grams are in a mole of sodium sulfate (Na₂SO₄)? Assume the following atomic weights: Na= 23, S= 32, and O= 16) a. 50g b. 94g c. 142g d. 284g

c. 142g

A BOD test was performed using a 300 milliliter bottle. Given the following measurements, calculate the BOD₅ in mg/L. -dissolved oxygen on Day 0= 8.1mg/L -dissolved oxygen on Day 5= 3.4mg/L -Volume of sample= 50mL a. 4.7 mg/L b. 15.7 mg/L c. 28.2 mg/L d. .8 mg/L

c. 28.2 mg/L

If you perform a 1:2 dilution on a 100 mg/L solution, what is the final concentration? a. 200mg/L b. 300mg/L c. 33mg/L d. 50mg/L

c. 33mg/L

What is the best glassware to use to accurately measure 43 mL of. a liquid? a. 50mL beaker b. 50mL volumetric flask c. 50ml graduated cylinder d. test tube

c. 50ml graduated cylinder

Which of the following is the best procedure to make a 100 milligram per liter solution using powdered Chemical X? a. add 100 mg to 1 liter of water in a beaker and mix b. put 100 mg into a beaker, fill to the 1 liter mark, and mix, c. add 100 mg to a volumetric flask containing some water mix then fill the flask to the 1 liter mark, and mix again d. place a beaker containing 1 liter of water on a balance, add the solid until the balances hows 1000.1 grams, and then mix

c. add 100 mg to a volumetric flask containing some water mix then fill the flask to the 1 liter mark, and mix again

What is the charge on the chloride ion (n) in the following reaction: FeCl₃→Fe³ + 3Clⁿ a. ⁺1 b. ⁻3 c. ⁻1 d. ⁺3

c. ⁻1

What relationship exists between the sample concentration and a parameter that the instrument measures such as color intensity or voltage?

calibration curve

How many grams of potassium iodide (KI) would you need to make 2 liters of a 0.075 M KI solution given that the molecular weight of KI= 166g/mole? a. 12.45g b. .90g c. 6.23g d. 24.90g

d. 24.90g

Which of the following statements is true? a. TSS= TS-NTU b. TSS= TS-VSS c. TSS= TDS-EC d. TSS= TS-TDS

d. TSS= TS-TDS

What should you do to convert liters to gallons?

divide the number of liters by 3.785

When using the hot plate, which action should be avoided?

putting wet glassware on a heated hot plate

What does BOD measure?

the mass of oxygen used to degrade organic substances in a sample

What is the most important feature to look for when obtaining a representative sample of wastewater flow containing suspended solids?

the right degree of mixing

What is the defining characteristic of organic compounds?

they contain carbon atoms

How are fire blankets used?

to smother clothing fires

In case of a spill, what action should you take?

use baking soda to neutralize acids and vinegar to neutralize bases

When would a grab sample be preferred over a composite sample?

when measuring constituents that change with time and the sample must be analyzed quickly