Hydrogen is a pure substance represented by the chemical symbol . Which of the following best describes hydrogen? A.
Hydrogen is an element made of two or more kinds of atoms.
B.
Hydrogen is a compound made of only one kind of atom.
C.
Hydrogen is an element made of only one kind of atom.
D.
Hydrogen is a compound made of two or more kinds of atoms.

What are similarities and differences of reflection, refraction, diffraction and absorption?

The ratio of lift to drag l/d for a wing or airfoil is an important aerodynamic parameter, indeed, it is a direct measure of the aerodynamic efficiency of the wing. if a wing is pitched through a range of angle of attack, l/d first increases, then goes through a maximum, and then decreases. consider an infinite wing with an naca 2412 airfoil. estimate the maximum value of l/d. assume that the reynolds number is 9x10^6.

Nacidified solution was electrolyzed using copper electrodes. a constant current of 1.18 a caused the anode to lose 0.584 g after 1.52 ✕ 103 s. given that the charge of an electron is 1.6022 ✕ 10−19 c, calculate avogadro's number. assume that copper is oxidized to cu2+ ions.