Calculate the change in internal energy (ΔE) for a system that is giving off 45.0 kJ of heat while 855 J of work is being performed on it from the surroundings.  

Which statement is true of the internal energy of a system and its surroundings during an energy exchange with a positive ΔEsys? 

Which compound has the weakest carbon—carbon bond?

(20 points total, 4 pts each) Draw the Lewis dot structure with formal charges (if it has any) of the following molecules (if there are resonance structures, you only need to draw one of them): HBr [NO3]- H2S CBr4 CO       

Correctly assign a formal charge to the nitrogen atom of the thiocyanate ion [SCN]- shown below. 

Which of the covalent molecules does not contain a carbon—oxygen double bond? 

Which compound has the shortest carbon—carbon bond length?

For ΔEsys to always be negative, what must be true?

Which of the following molecules do not have a dipole moment?   CH4   SF6 NH3 CO2 H2O I II III IV V  

Which of the following molecular geometries can be described as containing a central atom that possesses one lone pair of electrons?   tetrahedral T-shaped seesaw square planar square pyramidal I II III IV V