a radio actice substance decays so that half of the substance decays every 2 minutes. if 100 g of the substance are present initially, how many grams will be present after 4 minutes and 8 minutes respectively?
well if u have 100 g to start and half decays in 2 minutes so after 2 minutes u have 50 g then 4 minutes 25 grams then 6 minutes u have 12.5 g then 8 minutes u have 6.25 grams..you just divide ur original amount by two than that number by 2 (for every 2 minutes)
25,6.25
To determine the amount of radioactive substance that remains after a certain period of time, we can use the concept of half-life. The half-life is the time it takes for half of the substance to decay.
In this case, the half-life of the radioactive substance is 2 minutes. This means that after every 2 minutes, the amount of substance remaining will be halved.
Let's calculate the amount of substance remaining after 4 minutes:
After 2 minutes, half of the substance will decay, leaving us with 50 grams of the substance.
After another 2 minutes (a total of 4 minutes), another half will decay, leaving us with 25 grams of the substance.
So, after 4 minutes, 25 grams of the substance will be present.
Now let's calculate the amount of substance remaining after 8 minutes:
After the first 2 minutes, we have 50 grams.
After the next 2 minutes, we have 25 grams.
After the following 2 minutes, we have 12.5 grams.
After the last 2 minutes (a total of 8 minutes), we have 6.25 grams.
Therefore, after 8 minutes, 6.25 grams of the substance will be present.
To summarize:
- After 4 minutes: 25 grams
- After 8 minutes: 6.25 grams