Select all of the following which are examples of physical change.
change of composition
creation of a new substance
change of appearance
change in size and shape of a substance
change in phase of a substance
expansion or contraction of a substance

Agas mixture with a total pressure of 745 mmhg contains each of the following gases at the indicated partial pressures: co2, 245 mmhg ; ar, 119 mmhg ; and o2, 163 mmhg . the mixture also contains helium gas. part a what is the partial pressure of the helium gas? phe p h e = nothing mmhg request answer part b what mass of helium gas is present in a 10.2-l sample of this mixture at 283 k ? m m = nothing g request answer

In which direction will the following reaction go if the standard reduction potentials are 0.80 v for ag/ag+ and –0.44 v for fe/fe2+? ag+ + fe → ag + fe2+ a.)forward b.)the reaction cannot occur. c.) not enough information is given. d.) reverse

The ammonia molecule in the diagram has the observed bond orientation because