Answer: Sunlight.
Explanation:
Photochemical smog is formed when primary pollutants such nitrogen oxides and volatile organic compound (VOC) react with sunlight, forming a brown haze above cities.
Photochemical smog can only occur during the day.
Answer:

Explanation:
The question will be easier to solve if we interpret it as, " How long will it take until one-fourth of a sample of the element remains,?"
The half-life of the element is the time it takes for half of it to decay.
After one half-life, half (50 %) of the original amount will remain.
After a second half-life, half of that amount (25 %) will remain, and so on.
We can construct a table as follows:


Answer:
The initial temperature of helium was T1 = 232.23 K
Explanation:
Given data:
Initial volume V1 = 5 L
Initial pressure P1 = 699 mmHg
Final pressure P2 = 800 mmHg
Final volume V2 = 5.7 L
Final temperature T2= 303 K
Initial temperature T1 = ?
Solution:
Formula:
P1V1/T1 = P2V2/T2
T1 = T2 × P1V1/P2V2
T1 = 303 K × 699 mmHg × 5 L / 800 mmHg × 5.7 L
T1 = 1058985/ 4560
T1 = 232.23 K
initial temperature of helium was 232.23 k.
The substance is most likely a molecular compound