Answer:Artificial light from cities has created a permanent "skyglow" at night, obscuring our view of the stars. Here's their map of artificial sky brightness in North America, represented as a ratio of "natural" nighttime sky brightness. In the black areas, the natural night sky is still (mostly) visible.
Explanation:
Answer:
this is because spreading it makes more sunlight hit the cloth which results in it drying faster
b. testing the hypothesis
Answer:
19.4 g of alum, will be its theoretical yield
Explanation:
The reaction is:
2 Al + 2 KOH + 4 H₂SO₄ + 22H₂O → 3H₂ + 2KAl(SO₄)₂•12H₂O
Let's determine the amount of acid.
M are the moles contained in 1 L of solution or it can be mmoles that are contained in 1 mL of solution
M = mmol /mL
M . mL = mmol
We replace: 8.3 mL . 9.9 M = 82.17 mmoles
We convert to moles: 82.17 mmol . 1 mol / 1000mmol = 0.082 moles
Ratio is 4:2
4 moles of sulfuric acid can make 2 moles of alum
By the way, 0.082 moles of acid may produce ( 0.082 . 2) /4 = 0.041085 moles.
We convert moles to mass:
Molar mass of alum is: 473.52 g/mol.
0.041085 moles . 473.52 g/mol = 19.4 g
