Envirochemistry Review #2

Which is the smallest amount of a pollutant?

• 1 ppm (parts per million)

• 1 ppb (parts per billion)

• 1 ppt (parts per trillion)

• 1 part per thousand

What is the concentration of a solution in parts per million if 0.02 grams of NaCl is dissolved in 1000 grams of water?

• 2 ppm

• 20 ppm

• 200 pm

• 0.2 ppm

Which of the following concentrations is higher?

• 0.2 ppm

• 2.2 ppm

• 20.2 ppm

• 200 ppm

What is the concentration of solution (in ppm) made up of 0.005 grams of solute in 350 grams of solution?

• 14.3 ppm

• 12.1 ppm

• 1.4 ppm

• 9.8 ppm

There are 50 mg of salt in 8,000 mg of water. Write them in ppm.

• 160ppm
• 40,000ppm
• 4,000ppm
• 6,250ppm

Which is the highest concentration of lead?

• 5 ppm

• 0.5 ppm

• 5 ppb

• 0.5 ppb

How do scientists determine the toxicity of a chemical? 

• LD50 - expose it to many lab animals at different concentrations 
• wait for reports of death and mayham 
• Its chemical structure 
• which country it is from 

Which of the following statement about the LD50 is correct?

• The more toxic a substance is, the higer its LD50 would be
• LD50 is a measurement to COMPARE the toxicity with other substances
• LD50 is measured by testing toxins on humans

• LD50 stands for Lethal dose 50 mg/L

What is more dangerous? An LD50 of ...

• 0.04 ppm

• 1.29 ppm

• 1.04 ppm

• 0.40 ppm

Lethal dose (LD₅₀) values are determined by the amount of a substance that:

• kills at least 50 individuals of the test population exposed to the substance

• kills a test population when given at least 50 ml of the substance

• kills at least 50% of the test population exposed to the substance

• kills a test population when given at least 50g of the substance