In the reaction represented by the equation HF + H 2 O H 3 O+ + F- , a conjugate acid-base pair is: A. HF and H2O. B. F– and H3O+. C. H3O+ and H2O. D. HF and H3O+.

Hot air balloons float in the air because of the difference in density between cold and hot air. in this problem, you will estimate the minimum temperature the gas inside the balloon needs to be, for it to take off. to do this, use the following variables and make these assumptions: the combined weight of the pilot basket together with that of the balloon fabric and other equipment is w. the volume of the hot air inside the balloon when it is inflated is v. the absolute temperature of the hot air at the bottom of the balloon is th (where th> tc). the absolute temperature of the cold air outside the balloon is tc and its density is ďc. the balloon is open at the bottom, so that the pressure inside and outside the balloon is the same. as always, treat air as an ideal gas. use g for the magnitude of the acceleration due to gravity.

What is the number of moles of chemical units represented by 9.03x10^24? and how do i show work? (dumb it down )

Marcel just purchased 1.69 grams of iron fillings in order to make living putty for his 6 year old niece. how many moles of iron are made in his sample?