The sign (+ or -) of deltaH is___and the sign (+ or -) of deltaS is___for the ev

Question

The sign (+ or -) of deltaH is___and the sign (+ or -) of deltaS is___for the evaporation of water. Explain Chemical and physical changes can be classified as spontaneous or nonspontaneous. At 25degreeC and 1 atm pressure the decomposition of water into hydrogen and oxygen is classified as___, and the melting of ice is classified as___, Explain. A reaction for which deltaHdegree = + 98.8 kJ and deltaSdegree = + 141.5 J/K is___(spontaneous or nonspontaneous) at low temperatures and___(spontaneous or nonspontaneous)at high temperatures. Explain A 1.0 mole sample of gas at STP has a (lower/higher)___entropy than 1.0 mole of gas at 273 K and 835 mm Hg. Explain The entropy of water at 25degree is (less/greater)___than the entropy of water at 35degreeC. Explain

Explanation / Answer

6-delta H= -ve , delta S= +ve

for evoparation water absorbe energy to change its phase so delta H=-ve.

water under goes less odered state so delta S=+ve

7-Melting of ice is spontaneous bcause it takes place naturally without any outside intervention.

Decomposition of water is nonspontaneous because electricity is required to convert H2O to H2(g) and O2(g).

8-deltaH= + 98.8KJ   delta S = 141.5J/K

G=HTS

IfG<0 (negative), thereaction/processis spontaneous.

IfG<0 (posative), thereaction/processis nonspontaneous.

so at high temperature reaction is spontaneousthe term TS becomes greater than H and G becomes -ve.

at low temp reaction is nonspantaneous

9- Entropy is a measure of molecular disorder .

at STP T=273.15K P=1atm=760mm

so entropy is higher at STP since pressure is lower so molecules are more diodered.

10-less, because at high temperature molecules of water are more disodered at higher temp.

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