some chem questions (5)?

Question

10. The 1st law of thermodynamics states that:
a)Molecules move faster as temperature increases
b)The total energy of the universe is constant
c)Energy transfers from hotter objects to cooler objects
d)Samples with different temperatures that come in contact with one another will reach thermal equilibrium
e)All of the above

13. When 10g sample of the following materials absorb 100 J of heat, the temperature increase indicated is observed. Which material ha the largest specific heat?
a)water 2K
b) wood 6K
c) copper 26k
d) cement 11K
e) glass 12K

15. Determine the heat of vaporization of Titanium(IV)chloride given the enthalpies of reaction below.
Ti(s) + 2Cl2(g) --> TiCl3(l) delta heat= -804.2KJ
Ti(s) + 2Cl2(g) --> TiCl3(g) delta heat= -763.2KJ

Answer 1

1. B, The first law of thermodynamics is an expression of the universal law of conservation of energy, and identifies heat as a form of energy. The most common enunciation of first law of thermodynamics is:The increase in the internal energy of a thermodynamic system is equal to the amount of heat energy added to the system minus the work done by the system on the surroundings.
2. A, higher sp. heat means that more energy is required to change the temperature of a specific substance by 1 deg Celsius, thus if a material temp changes but low magnitude then it has highe sp.heat
3.41 kJ, look at the state of the product, your talking of vaporization then it would be liquid to gas, however, where is the liquid state? revert the 1st eqn then yuo'll have liquid state in the reactant side then add the 2 eqns. (the sign of the value in the 1st eqn will change also)

best answer?

Answer 2

10. (b) is the right answer

13. (a) because the same amount of mass absorbing the same amount of energy but has the lowest increase of temperature.

15. Invert the first equation and then add the two equations:

TiCl4(l) --> Ti(s) + 2Cl2(g) ΔH = 804.2 kJ
Ti(s) + 2Cl2(g) --> TiCl4(g) ΔH = -763.2 kJ
---------------------------------------------------------
TiCl4(l) --> TiCl4(g) ΔH = 41 kJ

Answer 3

1 e
2 a
3 -763.2 KJ