Real-Life Math
You're testing the levels of various chemicals in the air. Typically, when you report air concentrations, you want to get parts per billion. Your calculations give you micrograms per cubic meter.
You need to convert that number to parts per billion. That is, you're going to find out how many parts of chemical are in the air for every 1 billion parts of air.
Typically, when you report air concentrations, you want to get to parts per billion. Regulations for safe levels of chemicals are generally in parts per billion.
Things like atmospheric pressure change how many micrograms per cubic meter there are from one place to another. But parts per billion should stay the same.
To calculate parts per billion, you use a simple formula. You take the number of micrograms per cubic meter, multiply it by 24.45, and then divide the total by the gram molecular weight of the substance.
For both of the substances below, calculate the parts per billion.
- You have 100 micrograms per cubic meter of formaldehyde, an irritating chemical. It has a gram molecular weight of 30.
- You have 150 micrograms per cubic meter of naphthalene, which is used in mothballs. It has a gram molecular weight of 128.