Question

A.The heat change in a chemical reaction at constant _____________ is quantitatively expressed as the change of the enthalpy for the reaction.

temperature

volume

pressure

amount of mole

B.What will be final temperature if you mix the 50.g of water at 0.0oC to 50.g of water at 100.0oC.

75.0 degree Celsius

20.0 degree Celsius

90.0 degree Celsius

50.0 degree Celsius

C.Which will be the range of final temperature, Tfinal (oC) if you mix the 50.g of Magnesium metal (S=1.020 J/goC) at 0.0oC to 50.g of water (S=4.18 J/goC) at 100.0oC.

Tf > 100

50< Tf < 100

25< Tf < 50

0< Tf < 50

Tf < 50

D.The dissolution of ammonium sulfate by mixing a 20.g of ammonium sulfate with 20.g of water at same temperature will be an ______ process so that the final temperate of SURROUNDING solution will be LOWER than the initial temperature.

endothermic

equalthermic

exothermic

Answer 1

A)

Since, most chemical reactions occurs at constant pressure, so, heat change for a reaction at constant pressure is equals to enthalpy change for the reaction, which ia generally represented as,

Delta H(reaction) = delta H (products) - delta H (reactants)

Therefore, pressure ie option 3rd is the correct choice.

B)

Since, in the process

Heat lost = heat gained

-m x c x dT = m x c x dT

Putting the respective values, we get

50g x 4.18 J/g°C x (100 - T2)°C = 50 g x 4. 18 J / g°C x ( T2 - 0)°C

2 x T2 = 100 °C

T2 = 50° C

Therefore, option 4th is the correct choice.