Answer: 1 mole ➡️ 6.022×10²³ atoms of si.
X mole ➡️ 2.8×10²⁴ atoms of si.
X = 2.8×10×10²³/6.022×10²³
= 28/6.022
= 4.65 moles.
Explanation:
Answer:
explanation below
Explanation:
Dichlorodiphenyltrichloroethane, also known as DDT is a chemical compound that is found in insecticides. In 1972, the United States Environmental Protection Agency issued an order for the cancellation of requests for the chemical compound because it affects wildlife and pose risks to humans as well.
From the question here, it was noted that the initial concentration was 22ppm 25years ago and so if it takes 7years to decay by half, the actual concentration in present day farmers could be calculated as follows;
25years ago - 22ppm
18years ago - 11ppm
11years ago – 5.5 ppm
4 years ago - 2.75ppm
Since 7yrs = 0.5
Then 4yrs will be [ [4/7] x 0.5] = 0.2857
Then if 0.5 = 2,
Then 0.2857 = [ [ 0.2857/0.5] x 2] = 1.1428
So present year concentration would then be [2.75ppm/1.1428] = 2.406ppm
Answer:
The frequency
Step-by-step explanation:
The formula for the energy of an electromagnetic wave is
E = hf Thus,
E ∝ f and
f ∝ E
Answer:
A) 60
Explanation:
Given data:
Distance traveled by car = 210 km
Time taken = 3.5 hour
Speed of car = ?
Solution:
Formula:
S = d/t
s = speed of car
d = distance
t = time
by putting values,
s = 210 km / 3.5 hour
s = 60 km/hour
In order to get the sum of 2.7 and 2.47, we will add both numbers. So, 2.7 plus 2.47 would be 5.17. And the correct number of significant digits in this number is still the same, 5.17, so we have three significant numbers. Why? There are three rules in identifying the significant figures: 1. Non zeros are always significant (which this applies in our sum above). 2. Any zeros in between significant numbers are always significant. 3. <span> The final zero or zeros in the decimal portion only are significant.</span>