Answer:
See explanation below
Explanation:
To solve this problem, we need to use the expression of half life decay of concentration (or mass) which is the following:
m = m₀e^-kt (1)
In this case, k will be the constant rate of this element. This is calculated using the following expression:
k = ln2/t₁/₂ (2)
Let's calculate the value of k first:
k = ln2/2.7 = 0.2567 d⁻¹
Now, we can use the expression (1) to calculate the remaining mass:
m = 8.1 * e^(-0.2567 * 2.6)
m = 8.1 * e^(-0.6674)
m = 8.1 * 0.51303
m = 4.16 mg remaining
Light travels at precisely <span>299,792,458 metres every second (abbreviated to 3 x 10^8 metres every second but let's be precise)
There are 60 seconds in every minute (</span><span>299 792 458 x 60 = 17,987,547,480m)
60 minutes in every hour (17,987,547,480 x 60 = 1,079,252,849,000m)
96 hours in 4 days (</span><span>1,079,252,849,000 x 96 = 10,360,827,350,000m)
</span><span>Now let's convert to km to make this number (slightly) more manageable
(</span>10,360,827,350,000 / 1000 = <span>103,608,273,500km)
</span>Light travels <span>103,608,273,500km in 4 days - that's the equivalent of going around the equator of the earth 813,124 times!</span><span>
</span>
Answer:
after 45 days 9 g left
Explanation:
Given data:
Half life Na-24 = 15 days
Mass of sample = 72 g
Mass remain after 45 days = ?
Solution:
Number of half lives passed:
Number of half lives = time elapsed / half life
Number of half lives = 45 days / 15 days
Number of half lives = 3
At time zero total amount = 72 g
After first half life = 72 g/ 2= 36 g
At 2nd half life = 36 g/2 = 18 g
At 3rd half life = 18 g/2 = 9 g
Thus after 45 days 9 g left.
