Which processes represent one chemical change
and one physical change?
(1) freezing and melting
(2) freezing and vaporization
(3) decomposition and melting
(4) decomposition and combustion

The identities of substances are the same before and after which type of change

At a certain temperature the rate of this reaction is first order in hi with a rate constant of : 0.0632s2hig=h2g+i2g suppose a vessel contains hi at a concentration of 1.28m . calculate how long it takes for the concentration of hi to decrease to 17.0% of its initial value. you may assume no other reaction is important. round your answer to 2 significant digits.

For the reaction i2(g)+br2(g)←−→2ibr(g), kc=280 at 150 ∘c. suppose that 0.450 mol ibr in a 2.00-l flask is allowed to reach equilibrium at 150 ∘c. what is the equilibrium concentration of 2ibr, i2, br2