Ne(g)
is monoatomic (inert gas). Therefore heat of formation is zero.
For which of the following substances enthalpy of formation is zero?
The enthalpy of both
graphite and diamond
is taken to be zero, being elementary substances.
For which of the following substances does Δhof 0?
ΔHf° = 0 for elements in their standard states.
Carbon exists
naturally as solid graphite. Yes.
Which of the following substances ΔF h0 is not zero?
diamond is not zero.
Which of the following is not a state function?
Work
is not a state function as it depends upon the path followed.
What is Hess’s law used for?
Hess’ law can be used
to determine the overall energy required for a chemical reaction
, when it can be divided into synthetic steps that are individually easier to characterize. This affords the compilation of standard enthalpies of formation, that may be used as a basis to design complex syntheses.
What is the heat content of a system?
The total heat content of a system at constant pressure
is equal to the sum of the internal energy and PV
. This is called the enthalpy of a system which is represented by H. Note that enthalpy is also called as heat content.
Which substance has an enthalpy of formation of zero quizlet?
The enthalpy of a reaction and the enthalpy of the reverse reaction are equal. The enthalpy of a reaction is the negative of the enthalpy of the reverse reaction. Which substance has an enthalpy of formation of zero?
N2(g)
(The enthalpy of formation of an element in its standard state is zero.
What is the enthalpy of reaction 2 NO G O2 G 2 NO2 G ?
1/2N2 (g) + O2 (g) → NO2 (g), ΔH°A =
33.2 kJ 2
.
What is the standard enthalpy of reaction co h2o co2 h2?
The standard enthalpy of reaction is
+2.85 kJ
.
Does O have a heat of formation equaling zero?
The standard enthalpy of formation of any element in its standard state is zero by definition
. For example, although oxygen can exist as ozone (O
3
), atomic oxygen (O), and molecular oxygen (O
2
), O
2
is the most stable form at 1 atm pressure and 25°C.
Which has a value of zero at 25 C?
Graphite
and diamond are both forms of elemental carbon, but because graphite is more stable at 1 atm pressure and 25°C, the standard state of carbon is graphite (Figure 7.8. 1). Therefore, O2(g), H2(g), and graphite have ΔHof values of zero.
Which of the following has a DH f 0 kJ mol?
| Compound ΔH f o | O 2 (g) 0 kJ/mol | C( graphite ) 0 kJ/mol | CO(g) -110.5 kJ/mol | CO 2 (g) -393.5 kJ/mol |
|---|
Which of the following is not a state variable?
The correct option is B)
Temperature
, pressure, volume are examples of state variables.
Which one of the following is not extensive state function?
The
internal energy
is a state function of a system, because its value depends only on the current state of the system and not on the path taken or processes undergone to prepare it.
Which of the following is not a state function internal energy?
Work
and internal energy are not state functions.
Does zero order reaction have zero Molecularity?
No,
the molecularity can never be zero
or a fractional number as it shows the number of reactants taking part in a reaction which can never be zero.
In which process work done is zero?
Isochoric process
: It is a thermodynamic process which takes place at constant volume. In such a process, the work done is zero.
Which substance has defined as 0 kJ mol?
| Compound ΔH f o | H 2 (g) 0 kJ/mol | H 2 O(g) -241.8 kJ/mol | HF(g) -271.1 kJ/mol | NO(g) 90.25 kJ/mol |
|---|
What is Hess law class 11?
The Hess’s law states
that the total enthalpy change during a complete chemical reaction is the same
regardless of the path taken by the chemical reaction. … Hess’s law can be seen as an application of the principle of conservation of energy.
What does negative enthalpy mean?
A negative ΔHof indicates that
the formation of a compound is exothermic—the amount of energy it takes to break bonds is less than the amount of energy that is released when making the bonds
.
Can heat capacity be negative?
If
the system loses energy
, for example, by radiating energy into space, the average kinetic energy actually increases. If a temperature is defined by the average kinetic energy, then the system therefore can be said to have a negative heat capacity.
What is the ΔFH value for CO2 g’in kJ mol quizlet?
Terms in this set (28)
The enthalpy of formation of gaseous carbon dioxide is
−393.5 kJ/mol
.
Which of the following has a heat of formation equaling zero quizlet?
Which of the following has an heat of formation equaling zero? Explanation:
Elements that are in their natural state have
an enthalpy of formation that is equal to zero. F2 is the only element on the list that is in its natural state.
What is the enthalpy of formation quizlet?
The change in heat enthalpy
when one mole of a substance is formed directly from its constituent elements
is known as enthalpy of formation.
What is the rate law for the reaction 2NO g )+ O2 G → 2NO2 G?
The rate law for 2NO(g) + O2(g) ⟶ 2NO2(g) is
rate = k[NO]2[O2]
.
What is the ΔFH value for H2O L in kJ mol?
| Compound ΔH f (kJ/mol) | H 2 O(l) -285.8 | H 2 O 2 (l) -187.6 | H 2 S(g) -20.1 | H 2 SO 4 (l) -811.3 |
|---|
What is the enthalpy of H2O?
The standard enthalpy of formation of H2O(l) is
-285.8 kJ/mol
.
What is the ΔfH value for CH4 g in kJ mol?
The standard enthalpy of formation (ΔfH°) at 298 K for methane, CH4(g), is
–74.8 kJ mol–1
.
What is the standard enthalpy of the reaction CH4 g2 O2 g2 CO2 g 2H2O L ?
Limitation of using average bond enthalpies We earlier calculated using average bond enthalpies that for the reaction CH4 + 2O2 → CO2 + 2H2O ΔH =
-708 kJmol-1
. The published value for ΔcHΘ for this reaction is -890 kJmol-1.
Is 2NO G O2 G 2NO2 G exothermic?
Assertion (A): For the reaction, 2NO (g) + O2 (g) 2NO2 (g) , increase in pressure favours the formation of NO2 Reason (R):
The reaction is exothermic
.
Why are bond enthalpy Reactus minus?
Re: Enthalpy question
For the reactants, bonds are broken and energy is needed for this to happen (endothermic, positive enthalpy change). For the products, bonds are formed, leading to a more stable state, so energy is released (exothermic) and
the changes in bond enthalpies are negative
.
Is kJ mol enthalpy?
The standard enthalpy of reaction is symbolized by ΔHo or ΔHo
rxn
and can take on both positive and negative values. The units for ΔHo are
kiloJoules per mole
, or kj/mol. The Standard State: The standard state of a solid or liquid is the pure substance at a pressure of 1 bar ( 10
5
Pa) and at a relevant temperature.
Why is HF of O2 zero?
The enthalpy of formation for an element in its elemental state will always be 0
because it takes no energy to form a naturally-occurring compound
. … When a substance is formed from the most stable form of its elements, a change in enthalpy takes place.
Why is the enthalpy of H2 zero?
For H2 enthalpy of formation is zero,
because it already is the most elementary form
. In the problem, however, it’s talking about hear of combustion, which is different — Hydrogen does release heat.
Is O2 g equal to zero?
Here, oxygen gas has its elements which are already present in the standard state. Therefore,
the standard enthalpy of formation of O2 is equal to zero in their standard states
as there is no change takes place.
What is the standard enthalpy of S8?
It is a naturally occurring compound, which means no energy is released or consumed during its formation. Hence, the standard enthalpy of formation of S8 is
zero
.
What is the standard enthalpy of formation of liquid methanol?
| Species Name Formula Δ f H°(298.15 K) | Methanol CH3OH (l) -238.42 |
|---|
