Rubidium's atomic mass is 85.47. List the two most reasonable isotopes of rubidium. Which one should be more common? A common radioactive isotope of carbon is carbon-14. How many protons and neutrons does it have?

(Please at least answer ONE of the questions, both would be great though.)

8.98 dm3 of hydrogen gas is collected at 38.8 °c. find the volume the gas will occupy at -39.9 °c if the pressure remains constant.

The combustion of methane, ch4, releases 890.4kj/mol. that is, when one mole of methane is burned,890.4 kj are given off to the surroundings. this meansthat the products have 890.4 kj less than the reactants.thus, ah for the reaction = - 890.4 kj. a negative symbolforah indicates an exothermic reaction.ch (g) + 20 (g)> co2 (g) + 2 h0 (1); ah = - 890.4 kga) how much energy is given off when 2.00 mol of ch,are burned? b) how much energy is released when 22.4g of ch. areburned?

Jill is pushing a box across the floor. which represents the upward force perpendicular to the floor? a) fp b) ff c) fn d) fg