Answer: A. -396 kJ
Explanation:
The standard enthalpy of formation or standard heat of formation of a compound is the change of enthalpy during the formation of 1 mole of the substance from its constituent elements, with all substances in their standard states.
Reversing the reaction, changes the sign of 
On multiplying the reaction by 2, enthalpy gets multiplied by 2:
Thus the enthalpy change for the reaction is -396 kJ.
So that other scientist can repeat their experiments
i hope i got i right
we need the three measurements to be able to asses significant figures.
Answer:
4.48
Explanation:
p[OH-] = - log(3.00 *10^-10) = 9.52
pH + pOH = 14
pH = 14 - 9.52= 4.48
The dry ice absorbs heat from the air in the flask and become CO2 gas directly. So the heat flow from air to dry ice. And the CO2 gas increase the amount of the air. Though the temperature decreases, the balloon still inflates.
