Q: What is the change of entropy for 3.0 kg of water when the 3.0 kg of water is changed to ice at 0 °C? (Lf = 3.34 x 105 J/kg)
Answer:
-3670.33 J/K
Explanation:
Entropy: This can be defined as the degree of randomness or disorderliness of a substance. The S.I unit of Entropy is J/K.
Mathematically, change of Entropy can be expressed as,
ΔS = ΔH/T ....................................... Equation 1
Where ΔS = Change of entropy, ΔH = heat change, T = temperature.
ΔH = -(Lf×m).................................... Equation 2
Note: ΔH is negative because heat is lost.
Where Lf = latent heat of ice = 3.34×10⁵ J/kg, m = 3.0 kg, m = mass of water = 3.0 kg
Substitute into equation
ΔH = -(3.34×10⁵×3.0)
ΔH = - 1002000 J.
But T = 0 °C = (0+273) K = 273 K.
Substitute into equation 1
ΔS = -1002000/273
ΔS = -3670.33 J/K
Note: The negative value of ΔS shows that the entropy of water decreases when it is changed to ice at 0 °C
It's called a compound because different elements are held together by a chemical bond.
double-displacement reaction
Explanation:
We have the chemical reaction:
Na₂S (aq) + Cd(NO₃)₂ (aq) → CdS (s) + 2 NaNO₃ (aq)
where:
(aq) - aqueous
(s) - solid
This is a double-displacement reaction because the reactants exchange atoms or group of atoms between themselves to form the products. To drive the reaction to the right, one of the products is a precipitate.
Generally we can express the double-displacement reaction as following:
AB + CD → AC + BD
Learn more about:
types of chemical reactions
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HCI is the limiting reactant, and 4.3 mol AICI3 can be formed.
