in both volume and temperature, as shown in the 1. Imagine a reaction that resul
ID: 1053947 • Letter: I
Question
in both volume and temperature, as shown in the 1. Imagine a reaction that results in a change diagram below. What is the sign of the work being done, and what is the sign of the enthalpy change involved in this reaction? EXPLAIN!!! 1 atm Reaction, 2. How much heat is released or absorbed (specify which!!!) if 233.0 g calcium oxide reacts with 200.0 g carbon according to the following reaction? cao (s) + 3C (s) CaC2 (s) + CO (g) rnn_ 464.4 kJ/mol 3, Determine the Hnn for the below reaction (see tables in your book): CH4(g) +O2(g) CO2(g) H2O(g) + o Eplgl wy evues a) Using Standard Enthalpy of formation (AH') b) Using Bond Dissociation Energies (D). c) Explain why the values should be the same for both of these calculations. be t same for both of these calculations 4. Stearic acid, C18H3602, is a fatty acid found in foods like meat and candy bars. If the t for stearic acid -948 kJ/mol, and a candy bar contains 11.0 g stearic acid, how many Nutritional calories (Cal) are coming from the fat in the candy bar? Use the enthalpy of formation table in your book as needed (Table 6.5). 02(g) COag) H2O(g) + 5.One of the components of polluted air that causes photochemical smog is NO (nitrogen monoxide). It is formed in the high-temperature environment of internal combustion engines in the reaction below. Why are high temperatures needed to convert N2 and O2 to NO? Discuss in relation to bonds. 6.Explain why ionization energy decreases as you move down the noble gases from Helium to argon. Sodium atoms are much larger than chlorine atoms, but sodium ions are much smaller than chloride ions. Why? 7.Explanation / Answer
1. For the process with both increase in volume and temperature,.
the sign for work = +ve
the sign for enthalpy = +ve
2. moles of CaO = 233/56.0774 = 4.155 mols
moles of C = 200/12.01 = 16.653 mols
Limiting reactant
If all of CaO is consumed, we would need = 3 x 4.155 = 12.465 mols of C
Since moles of C available is higher than required, CaO is the limiting reactant
Amount of heat absorbed = 4.155 x 464.4 = 1929.582 kJ
3. Calculation of enthalpy
a) dHrxn = (-393.51 - 241.82) - (-74.9) = -560.43 kJ/mol
b) dHrxn = (4 x 413 + 498) - (2 x 799 + 2 x 463) = -374 kJ/mol
c) The values for both these differ and are not the same.
6. Ionization energy is energy needed to pull off an electron from the valence shell of an atom. As we go down the group, we add additional shells to the atoms which increases the distance between nucleus and outer valence shell electrons in the atom. Thereby reduces the attractive forces between potively charged nucelus and negatively charged valence shell electrons. This therefore makes it easier for electrons to be pulled off and ionization energy thus decreases down the noble gas group.
7. Sodium atom is larger than Cl atoms. Once we remove an electron from Na to form Na+ ion, the net attractive force from the positively charged nucelus pulls in the outer eectrons more strongly. On the other hand adding an electron to the Cl to form Cl-, increases the electrons in the valence shell and +ve charged nucleus becomes insufficient to pull the additional electron due to charge imbalance. Thus Cl- is bigger and Na+ is smaller in size.
8. Xenon and Krypton are larger in size and thus outer valence shell electrons can be pulled off easily than other smaller atoms of noble gas series. Thus compounds of these two are possible but not of the others.
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