Why is human skin purple when uv light is shined on it?

Astudent reacts 13 moles of iron with 21 moles of oxygen according to the following equation:

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.

An object displaces 652 ml of water. the volume of the object is: 0.652 cm³ 6.52 cm³ 65.2 cm³ 652 cm³