Question

pleasee show me how to get the correct answers in preperation for my upcoming exam

2.) D 3.) B 4.) D

2) A 5.00-g sample of copper metal at 25.0°C is heated by the addition of 133 J of energy. The final temperature of the copper is °C. The specific heat capacity of copper is 0.38 J/g-K. A) 45.0 B) 25.0 C) 70.0 D) 95.0 E) 35.1 250 3) The value of AE for a system that performs 151 kJ of work on its surroundings and loses 79 kJ of heat is_ kl A) -72 B) -230. C) +72 D) -151 E) +230 4) The value of AH® for the reaction below is -126 kJ. The amount of heat that is released by the reaction of 10.0 g of Na202 with water is__ kJ 2Na2O2 (s) + 2H20 (1) 4NaOH (s) + O2 (8) A) 32.3 B) 67.5 C) -126 D) 8.08 E) 16.2

Answer 1

Q2)

$Q = mS\Delta T\\ \Delta T=Q/(mS)=133/(0.38\times 5)=70\\T_{2}-T_{1}=70\\T_{2}=T_{1}+70=25+70=95\\$

Ans.- D = 95

Q3)

$\\\Delta E=Q+W \\ W = -151 kJ\\ Q=-79 kJ\\ \Delta E= -151-79 -= -230 kJ$

W is negative as system performs work on the surroundings. Q is also negative as system releases heat.

Ans.- B = -230 kJ

Q4) From the reaction equation, it is seen that 2 moles of Na₂O₂ will produce 126 kJ heat.

Molecular weight of Na₂O₂ = 23 X 2 + 16 X 2 = 156

Hence, 156 g Na₂O₂ produce 126 kJ heat.

10 g Na₂O₂ will produce (126 X 10)/156 kJ heat = 8.08 kJ heat