A642 ml sample of oxygen gas at 23.5°c and 795 mm hg, is heated to 31.7°c and the volume of the gas expands to 957 ml. what is the new pressure in atm? a) 0.723 atm b) 0.932 atm c) 3.05 atm d) 5.19 atm

We can use the combined gas law equation to find the new pressure of the gas. 

where P - pressure 
V - volume
T - temperature 
parameters for the first instance are on the left side and parameters for the second instance are on the right side of the equation 
P1 - 795 mm Hg x 0.0013 atm/ mm Hg = 1.033 atm
T1 - 23.5 °C + 273 = 296.5 K
T2 - 31.7 °C + 273 = 304.7 K
substituting the values in the equation 

P = 0.712 atm 
the answer closest to this value is A) 0.723 atm
therefore answer is 
A)0.723 atm

(no3)⁻n has oxidation number x,o has oxidation number -2.(x*1 -2*3) charge of the nitrate ion, and we know that charge of the nitrate ion =-1.so,(x*1 -2*3) =-1x-6=-1x=+5answer a. +5.

Answeropposite;