Advertisements
Advertisements
प्रश्न
Answer the following in one or two sentences.
What is standard state of a substance?
Advertisements
उत्तर
- The standard state of a substance is the form in which the substance is most stable at a pressure of 1 bar and at a temperature of 298 K.
- If the reaction involves species in solution, its standard state is 1 M concentration.
e.g. Standard states of certain elements and compounds are (at 1 bar and 25 °C); \[\ce{H2_{(g)}, Hg_{(l)}, Na_{(s)}, C_{(graphite)}, C2H5OH_{(l)}, CaCO3_{(s)}, CO2_{(g)}, C2H5OH_{(l)}, H2O_{(l)}, CaCO3_{(s)}, CO2_{(g)}}\].
APPEARS IN
संबंधित प्रश्न
Select the most appropriate option.
Which of the following reactions is exothermic?
Answer the following question.
State Hess’s law of constant heat summation. Illustrate with an example. State its applications.
The enthalpy change for the reaction, \[\ce{C2H4_{(g)} + H2_{(g)} -> C2H6_{(g)}}\] is −620 J when 100 mL of ethylene and 100 ml of \[\ce{H2}\] react at 1 bar pressure. Calculate the pressure volume type of work and ΔU for the reaction.
Define the Standard enthalpy of combustion.
State and explain Hess’s law of constant heat summation.
The enthalpy change of the following reaction:
\[\ce{CH_{4(g)} + Cl_{2(g)} -> CH3Cl_{(g)} + HCl_{(g)}ΔH^0 = –104 kJ}\]
Calculate C – Cl bond enthalpy. The bond enthalpies are:
| Bond | C − H | Cl − Cl | H − Cl |
| ∆H°/kJ mol−1 | 414 | 243 | 431 |
Calculate the standard enthalpy of combustion of CH4(g) if ΔfH°(CH4) = – 74.8 kJ mol–1, ΔfH°(CO2) = – 393.5 kJ mol–1 and ΔfH°(H2O) = – 285.8 kJ mol–1.
Define standard enthalpy of formation.
Define the Bond enthalpy.
Does the following reaction represent a thermochemical equation?
\[\ce{CH_{4(g)} + 2O_{2(g)} -> CO_{2(g)} + 2H2O_{(g)}}\], ∆fH° = –900 kJ mol–1
A compound that has a high negative heat of formation is normally ____________.
The volume of oxygen required for complete combustion of 0.25 mole of methane at STP is ______.
The heat of formations of CO(g) and CO2(g) are −26.4 kcal and −94.0 kcal respectively. The heat of combustion of carbon monoxide will be ____________.
The standard heats of formation for CCl4(g), H2O(g), CO2(g), and HCl(g) are −25.5, −57.8, −94.1 and −22.1 kcal mol−1, respectively.
∆H for the reaction
\[\ce{CCl4_{(g)} + 2H2O_{(g)} -> CO2_{(g)} + 4HCl_{(g)}}\] at 298 K
The enthalpy change accompanying a reaction in which 1 mole of the substance in the standard state reacts completely with oxygen or is completely burnt is called as ____________.
Enthalpy of formation of two compounds x and y are −84 kJ and −156 kJ respectively. Which of the following statements is CORRECT?
Calculate the enthalpy of hydrogenation of C2H4(g), given that the enthalpy of formation of ethane and ethylene are −30.2 kcal and +12.5 kcal respectively.
An ideal gas expands isothermally and reversibly from 10 m3 to 20 m3 at 300 K performing 5 .187 kJ of work on surrounding. Calculate number of moles of gas undergoing expansion. (R = 8.314 J K-1 mol-1)
Heat of formation of water is - 272 kJ mol-1. What quantity of water is converted to H2 and O2 by 750 kJ of heat?
Standard entropies of N2(g), H2(g), and NH3(g) are a1, a2 and a3 J K-1 mol-1 respectively. What is value of ΔS° for formation of NH3(g)?
Heat of formation of ethane, ethylene acetylene and carbon dioxide are - 136, - 66, - 228 and - 395 (all in kJ) respectively, most stable among them is ______.
Calculate the standard enthalpy of formation of CH3OH(l) from the following data:
- \[\ce{CH3OH_{(l)} + 3/2 O2_{(g)} -> CO2_{(g)} + 2H2O_{(l)}ΔH^° = - 726 kJ mol^{-1}}\]
- \[\ce{C_{(s)} + O2_{(g)} → CO2_{(g)}Δ_cH^° = – 393 kJ mol^{-1}}\]
- \[\ce{H2_{(g)} + 1/2 O2_{(g)} -> H2O_{(l)}Δ_fH^° = - 286 kJ mol^{-1}}\]
When 0.5 gram of sulphur is burnt to form SO2, 4.6 kJ of heat liberated. Calculate enthalpy of formation of SO2(g). (Atomic mass : S = 32, O = 16)
Which of the following reactions defines the enthalpy of formation?
Calculate ΔsubH of the H2O from the given data:
\[\ce{H2O_{(s)}->H2O_{(l)},}\] ΔfusH = 6.01kJ mol−1
\[\ce{H2O_{(l)}-> H2O_{(g)},}\] ΔVapH = 45.07 kJ mol−1.
Calculate heat evolved for combustion of 13 gm of acetylene (C2H2).
Given: \[\ce{C2H2_{(g)} + 5/2O_{2(g)}-> 2CO_{2(g)} + H2O_{(l)} \Delta_{(c)}H^{0} = - 1300 kJ}\]
Heat of combustion of CH4(g) is -890 kJ/mole. What is the value of Δc H of 8gm of methane?
