Air contains 79% nitrogen and 21% oxygen by volume what is the molar fraction of oxygen in air? (ignore any other minor gases in air) A: 0.24
B: 0.18
C: 0.79
D. 0.21

Afamily is one another name for a group on the table of elements.

An animal cell loses the ability to convert energy stored in food to energy that the cell can use. which of the cell's organelles has stopped working? a.the mitochondria b.the nucleus c.the vacuoles d.the endoplasmic reticulum

Abeaker with 2.00×102 ml of an acetic acid buffer with a ph of 5.000 is sitting on a benchtop. the total molarity of acid and conjugate base in this buffer is 0.100 m. a student adds 4.70 ml of a 0.360 m hcl solution to the beaker. how much will the ph change? the pka of acetic acid is 4.740.