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What is the enthalpy and entropy change when ammonium chloride is dissolved in water?
Wiki User
∙ 12y ago
The published value for an enthalpy change is 14.78 kJ/mol
Wiki User
∙ 12y ago
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If water H2O is polar and oxygen O2 non-polar how can there be dissolved oxygen in water?
The simple answer is that most everything happens at least a little bit. The reason why is EQUILIBRIUM. You are correct---water is polar and oxygen is non-polar. The water molecules have great hydrogen bonding and dipole-dipole interactions with each other that the oxygen molecules cannot replace, and so it will take energy or ENTHALPY for oxygen to mix its way into the water. So the process is ENDOTHERMIC and hence unfavorable. However, when you dissolve oxygen in water, you get disorder---something that scientists quantify by talking about a solution's ENTROPY. It is favorable for entropy to increase, and in this case the entropy of the water solution would go up if you were to be able to squeeze some water molecules in there. So entropy and enthalpy are at odds for this reaction. Enthalpy is unfavorable, entropy is favorable. In situations like that systems will reach a state of equilibrium in which the reaction partially occurs. How much will depend on the relative sizes of the entropy and enthalpy changes.
Why NaCl is very soluble but not CaO is only slightly soluble in water?
Its all to do with enthlapy and entropy. Anything which is soluble usually has a negative standard enthlapy of solution - the energy involved when 1 mole of solute dissolves in a solvent to give an infinately dilute solution. However, NaCl has a slightly positive enthalpy of solution, yet it dissolves. The reason for this is entropy - the change in the amount of disorder. When NaCl dissolves in solution, there is more chaos, more molecules within the solution. Any process that has a large positive entropy change will be favourable - spontaneous and can occur (reaction will 'go'). However, with CaO, the Ca2+ formed in solution has a high affinity (attraction to) for water molecules, hence a lot of water molecules are arranged orderly - less chaos and hence a negative entropy. This should in effect make the compound insoluble, however, the slight solubility is due to it still having a negative enthalpy change of solution - hence despite entropy it is still slightly soluble. (You may be asking how is dissolving CaO possible if entropy is negative? The entropy of the system maybe negative, but the entropy of the surroundings is positive (dissolving gives out heat - exothermic), hence the overall entropy (sum of both entropies) is positive and the reaction will 'go'.
Calculate the entropy of vaporization per mole of ethanol Given enthalpy change is 109.8 JK-1 mol-1 and boiling point of ethanol is 78.50C?
OK.With entalpy od vaporization and temperature of vaporization is very easy to calculate entropy of vaporization of etanol.So the equation to calculate this is:Delta_S=-Delta_H/TbWhere:Delta_S= Entropy of vaporizationDelta_H=Entalpy of vaporizationTb= Normal Boiling point temperatureSo the Delta_S become:Delta_S=-(-109000.8)/(78.5+273)Delta_S=310.1 J.mol-1.K-1
The angle of the rays of the sun strike a broken bottle in a ditch at 10 00 am At 3 45 pm the surrounding dry grass catches fire Was this a spontaneous reaction?
Yes, this was a spontaneous reaction. A reaction is said to be spontaneous if it occurs without being driven by some outside force. There are two driving forces for all chemical reactions. The first is enthalpy, and the second is entropy.
What is the entropy change for the vaporization of 1.8 mol H2O at 100 degrees Celsius and 1 ATM?
I think you meant to use the word enthalpy. Enthalpy refers to the flow of heat, while entropy means the "randomness" of a system.Because The water is already at its boiling point (100o C), it doesn't need to be heated any more to start boiling. To find out how much energy it takes, you'll need to look up the molar heat of vaporization. Simply put, this is the amount of energy it takes to boil one mol of a substance. Water's molar heat of vaporization is 40.2 kJ/mol.Now, all we need to do is multiply:1.8mol * 40.2kJ/mol = 72kJ(Note: The 1 atm is important because that is the pressure at which water's boiling point is 100oC. If there was any less pressure, it would have already boiled. If there was more pressure, it would have to heat up to the new boiling point, then use 72kJ to boil.)
When graphing enthalpy and entropy what variables are included?
Temperature and energy are two of the variables included when graphing enthalpy and entropy. Enthalpy is made up of the energy, pressure, and volume of a system. Entropy is a way to determine the different ways energy can be arranged.
What characteristics of a substance is NOT affected by enthalpy and entropy?
Pressure is not affected by enthalpy and entropy.pressure
Is Delta S is the change in enthalpy a measure of randomness?
No, delta s is the change in entropy. Delta H is the change in enthalpy, the amount of heat used in a system. Entropy and enthalpy are different, but closely related.
How is energy permantely lost?
To feed the rise in Entropy. Enthalpy is a constant, but Entropy is always increasing.
Is polymerization endothermic or exothermic?
Exothermic, because the reaction enthalpy must be negative. With polymerization, the entropy decreases. The Gibbs energy has to be negative. Thus negative reaction enthalpy. Gibbs energy = reaction enthalpy - temperature*entropy
Does the entropy of a solid increases when its dissolved in a solvent?
Why does the entropy of a solid increases when it is dissolved in a solvent
What is the definition of enthalpy and entropy?
Enthalpy is the amount of energy released or used when kept at a constant pressure. Entropy refers to the unavailable energy within a system, which is also a measure of the problems within the system.
What factors generally determine whether a reaction happens or not?
Enthalpy and entropy.
Predict whether the changes in enthalpy entropy and free energy will be positive or negative for the freezing of water and explain your predictions How does temperature affect the spontaneity?
Enthalpy- positive Entropy- decreasing Free energy- negative
What kind of changes contribute to spontaneity?
An increase in entropy.
If water H2O is polar and oxygen O2 non-polar how can there be dissolved oxygen in water?
The simple answer is that most everything happens at least a little bit. The reason why is EQUILIBRIUM. You are correct---water is polar and oxygen is non-polar. The water molecules have great hydrogen bonding and dipole-dipole interactions with each other that the oxygen molecules cannot replace, and so it will take energy or ENTHALPY for oxygen to mix its way into the water. So the process is ENDOTHERMIC and hence unfavorable. However, when you dissolve oxygen in water, you get disorder---something that scientists quantify by talking about a solution's ENTROPY. It is favorable for entropy to increase, and in this case the entropy of the water solution would go up if you were to be able to squeeze some water molecules in there. So entropy and enthalpy are at odds for this reaction. Enthalpy is unfavorable, entropy is favorable. In situations like that systems will reach a state of equilibrium in which the reaction partially occurs. How much will depend on the relative sizes of the entropy and enthalpy changes.
What could make G become negative at a given enthalpy and entropy?
Changing the temperature
