Chem: Thermochemistry

A liquid with a specific hear of 1.9 J/gC has 4750 J of energy added to it. The temperature changed from 20 degrees C to 30 degrees C, what is the mass of the liquid?

• 250 cal

• 2500cal

• 250 g

• 2500 cal

If 238 J of heat is absorbed by a sample of metal with a mass of 40.7 g, and it raises the temperature from 20.0°C to 32.4°C, what is the specific heat capacity of the metal? (show your work)

• 2.34 J/g°C

• 0.472 J/g°C

• 6.13 J/g°C

• 0.163 J/g°C

The specific heat(c) of copper is 0.39 J/g °C. What is the temperature change(∆t) when 100 Joules of heat(Q) is added to 20 grams?

• 12.82 °C

• 24.12°C

• 351 °C

A sample of iron receives 50.J of heat energy that raises the temperature of the iron 25.0°C. If iron has a specific heat of  0.10 J/g°C, what is the mass of the iron sample?

• 25 g

• 30 g

• 20 g

• 50 g

When 1500J of energy is lost from a 120 gram object, the temperature decreased from 45 degrees C to 40 degrees C. What is the specific heat of the object?

• 2.5 J/gC

• 1.5 J

• 12.5 Cal/gC

• 15 J/gC1 

The heat content of a system at constant pressure is called

• entropy

• enthalpy

• heat

• energy

Chemical reactions where both q and H are negative are considered

• spontaneous

• nonspontaneous

• exothermic

• endothermic

(Hess's Law)Calculate the ∆H for the following reaction: 2H₂O₂ →  2H₂O  + 1 O₂ 
You are given these two equations:
2H₂  +  O₂ → 2H₂O            ∆H  =  -572 kJ
H₂  +  O₂  →  H₂O₂            ∆H  =  -188 kJ 

• ∆H  =  -948 kJ 

• ∆H  =  -196 kJ 

• ∆H  =  -384 kJ 

• ∆H  =  -188 kJ 

The enthalpies of combustion of C(s), H2(g) and C4H9OH(l) (in kJmol^-1) are as follows  
C(s) + O₂(g)   ->  CO₂(g)                                               ∆H=a
H₂(g) + ½O₂(g)   ->   H₂O(l)                                        ∆H=b
C₄H₉OH(l) + 6O₂(g)   ->   4CO₂(g) + 5H₂O(l)  ∆H=c
What is the enthalpy change for the reaction shown below?
  4C(g) + 5H₂(l) + ½O₂(g)   ->   C₄H₉OH(l)

• c – 4a – 5b

• 2a + 10b - c

• 4a + 5b - c

• 2a + 5b + c

In an _________________ process, the system gains heat from its surrounding

• Endothermic

• Exothermic