List two observations that could be evidence of a chemical reaction.

1) Smell or odour

2) Colour change

Explanation:

1) Smell or odour

Example: Add HCl to a FeS solution. There will be a  strong odor of H2S

2) Colour change

Example : NaOH and KMnO4 solution to a river water sample. There will be  a colour change to brown.

what is the volume occupied by 40 grams of argon gas (ar) at standard conditions? what volume, in liters, is occupied by 1.5 x 1023 

in the given question, the partial pressure is calculated by using the ideal gas equation, that is, pv = nrt

here, p is pressure, v is volume = 25 l, n is number of moles = 0.0104 moles, r is gas constant = -0.0821 l.atm / mol.k

t is temperature = 273 k

p = nrt / v

p = (0.0104 mol × 0.0821 l.atm / mol.k × 273 k) / 25 l

= 0.0093 atm