1. The reactivity among the alkali metals increases as you go down the group due to the decrease in the effective nuclear charge from the increased shielding by the greater number of electrons. The greater the atomic number, the weaker the hold on the valence electron the nucleus has, and the more easily the element can lose the electron. Conversely, the lower the atomic number, the greater pull the nucleus has on the valence electron, and the less readily would the element be able to lose the electron (relatively speaking). Thus, in the first set comprising group I elements, sodium (Na) would be the least likely to lose its valence electron (and, for that matter, its core electrons).
2. The elements in this set are the group II alkaline earth metals, and they follow the same trend as the alkali metals. Of the elements here, beryllium (Be) would have the highest effective nuclear charge, and so it would be the least likely to lose its valence electrons. In fact, beryllium has a tendency not to lose (or gain) electrons, i.e., ionize, at all; it is unique among its congeners in that it tends to form covalent bonds.
3. While the alkali and alkaline earth metals would lose electrons to attain a noble gas configuration, the group VIIA halogens, as we have here, would need to gain a valence electron for an full octet. The trends in the group I and II elements are turned on their head for the halogens: The smaller the atomic number, the less shielding, and so the greater the pull by the nucleus to gain a valence electron. And as the atomic number increases (such as when you go down the group), the more shielding there is, the weaker the effective nuclear charge, and the lesser the tendency to gain a valence electron. Bromine (Br) has the largest atomic number among the halogens in this set, so an electron would feel the smallest pull from a bromine atom; bromine would thus be the least likely here to gain a valence electron.
4. The pattern for the elements in this set (the group VI chalcogens) generally follows that of the halogens. The greater the atomic number, the weaker the pull of the nucleus, and so the lesser the tendency to gain electrons. Tellurium (Te) has the highest atomic number among the elements in the set, and so it would be the least likely to gain electrons.
PV=nRT
P=nRT/V
P=[(0.650mol)(0.08206)(298K)]/(0.750L)=21.2atm
Answer :
121.5 <span>
μCi
Explanation : We have Ce-141 half life given as 32.5 days so if the activity is 3.8 </span><span>μci after 162.5 days of time elapsed we have to find the initial activity.
We can use this formula;
</span>
3.8 /
=
((0.693 X 162.5 ) / 32.5) = 121.5
<span>
On solving we get, The initial activity as 121.5 </span>μci
A condensation reaction is described to be a reaction wherein two molecules form an even larger product and consequently produces a smaller molecule as a by-product. For example, when two amino acids are combined, a dipeptide bond is formed. As a result, 1 molecule of water is produced as a by-product.
Answer:
Incomplete question, it is lacking the data it makes reference. The missing data from Chegg is:
2 SO3(g) → 2 SO2(g) + O2(g)
ΔHf° (kJ mol-1) -395.7 -296.8
S° (J K-1 mol-1) 256.8 248.2 205.1
ΔH° = kJ
S° = J K⁻¹
Explanation:
The method to solve this problem calls for the use of the Gibbs standard free energy change:
ΔG
= ΔrxnH - TΔSrxn
We know a reaction is spontaneous when ΔG is < 0, so to answer this question we need to solve for the temperature, T, at which ΔG becomes negative.
Now as mentioned in the hint, we need to determine ΔrxnH and ΔSrxn, which are given by
ΔrxnH = ∑ ν x ΔfHº products - ∑ ν x ΔfHº reactants
where ν is the stoichiometric coefficient in the balanced chemical equation.
For ΔS we have likewise
ΔrxnS = ∑ ν x ΔSº products - ∑ ν x ΔSº reactants
Thus,
ΔrxnH(kJmol⁻¹) = 2 x (-296.8) - 2 x ( -395.7 ) = 197.8 kJ
ΔrxnS ( JK⁻¹) = 2 x 248.2 + 205.1 - 2 x 256.8 = 187.9 JK⁻¹ = 0.1879 kJK⁻¹
So ΔG kJ = 197.8 - T(0.1879)
and the reaction will become spontaneous when the term T(0.1879) becomes greater that 197.8,
0 = 197.8 - 0.1879 T ⇒ T = 1052 K
so the reaction is spontaneous at temperatures greater than 1052 K (780 ºC)
