Is hydrogen gas a mixture or pure substance?

What is a possible quantum number set for an electron in the 3s orbital of a magnesium atom

Answer asap need to be answered by wednesday morning explain how a buffer works, using an ethanoic acid / sodium ethanoate system including how the system resists changes in ph upon addition of a small amount of base and upon addition of a small amount of acid respectively. include the following calculations in your i. calculate the ph of a solution made by mixing 25cm3 0.1m ch3cooh and 40cm3 0.1m ch3coo-na+. [ka = 1.74 x 10-5 m] ii. calculate the ph following the addition of a 10cm3 portion of 0.08 m naoh to 500cm3 of this buffer solution. iii. calculate the ph following the addition of a 10cm3 portion of 0.08 m hcl to 200cm3 of the original buffer solution.

Use the de broglie's wave equation to find the wavelength of an electron moving at 7.3 × 106 m/s. show your work. note: h = plank's constant (6.62607 x 10-34 j s)