One mole of solid cr2 o3 at 2500 k is dissolved in a large volume of a liquid raoultian solution of al2 o3 and cr2 o3 , in which xcr2o3 = 0.2 and which is also at 2500 k. calculate the changes in enthalpy and entropy caused by the addition. the normal melting temperature of cr2 o3 is 2538 k, and it can be assumed that δsm, al2o3 δsm, cr2o3 =

Asample of aluminum foil contains 8.60 × 1023 atoms. what is the mass of the foil?

3. how much energy in joules is required to evaporate .0005 kg of liquid ammonia to vapor at the same temperature? 4. how much energy ( in megajoules ) is given up by .75 kg of water at 0c when it freezes to form ice at 0c? 5. explain how heat works between and at critical temperatures?

Modern pennies are composed of zinc coated with copper. a student determines the mass of a penny to be 2.482 g and then makes several scratches in the copper coaling (to expose the underlying zinc). the student puts the scratched penny in hydrochloric acid, where the following reaction occurs between the zinc and the hcl (the copper remains undissolved): zn(s) + 2 hcl(aq) → h2(g) + zncl(aq)the student collects the hydrogen produced over water at 25 °c. the collected gas occupies a volume of 0.899 l at a total pressure of 79 j mmhg. calculate the percent zinc (by mass) in the penny. (assume that all the zn in the penny dissolves.)