Answer:
The answer is -791.5 kJ (option c)
Explanation:
You know:
SO₂ (g) → S (s) + O₂ (g) ΔH°rxn = +296.8 kJ
2 SO₂ (g) + O₂ (g) → 2 SO₃ (g) ΔH°rxn = -197.8 kJ
You must add them to obtain the desired equation:
2 S(s) + 3 O₂(g) → 2 SO₃(g) ΔH°rxn = ?
You want to calculate the ∆H (heat of reaction) of the combustion reaction, that is, the heat that accompanies the entire reaction. The calculation is made using Hess's law. This law states: when the reactants are converted to products, the enthalpy change is the same, regardless of whether the reaction is carried out in one step or in a series of steps.
In Hess's law he explains that the enthalpy changes are additive, ΔHneta = ΣΔHr and contains three rules:
-
If the chemical equation is inverted, the ΔH symbol is inverted as well.
- If the coefficients are multiplied, multiply ΔH by the same factor.
- If the coefficients are divided, divide ΔH by the same divisor.
The sum of the fitted equations should give the problem equation. In this case:
2*( S(s) + O₂(g) → SO₂ ) To obtain the desired reaction, this equation must be inverted, so the enthalpy value is also inverted. It must also be multiplied by 2, then the whole equation is multiplied, both reactants and products and the value of the enthalpy. So ΔH°rxn = (-296.8 kJ)*2= -593.6 kJ
2 SO₂(g) + O₂(g) → 2 SO₃ (g) ΔH°rxn = -197.8 kJ
____________________________________________________
2 S(s) + 3 O₂(g) → 2 SO₃(g) ΔH°rxn = -791.4 kJ (
Enthalpies are added algebraically)
<u><em>The answer is -791.5 kJ (option c)</em></u>
Answer:
We know that kinetic energy is one of the forms of internal energy, so the release of heat from an object causes a decrease in the average kinetic energy of its particles.
<span>These are the rules of the quantum numbers that you have to use to dilucidate the validity of a set of quantum numbers:
</span><span />
<span>1) Main quantum number, n: 1, 2, 3, 4, 5, 6, 7
</span>
<span /><span /><span>
2) Second quantum number, ℓ: 0, 1, 2, ... n-1
</span><span />
<span>3) Third quantum number (magnetic quantum number), mℓ: -l,...0,,,,+l
</span><span />
<span>4) Fourth quantum number (spin): ms: +1/2 or -1/2
</span>
<span /><span /><span />
Answers:
<span>i) 3,2,0,1/2: valid, because 0<= l < n; - l <= ml <= +l; and ms = +1/2 or -1/2
</span>
<span /><span /><span>
</span><span>ii) 2,2,-1, 1/2 invalid because l = n (violates second rule)</span><span /><span>
</span><span>
</span><span>iii) 4,3,-4,1/2 invalid because ml is less than - l (violates third rule)</span><span /><span>
</span><span>
</span><span>iv) 1,0,0,1/2 valid: meet the four rules</span><span /><span>
</span><span>
</span><span>v) 2,2,1,-1/2 invalid because l = n (violate the second rule)</span><span /><span>
</span><span>
</span><span>vi) 3,2,1,1 invalid because ms can be only +1/2 or -1/2 (fourth rule)
</span>
<span /><span /><span>vii) 0,1,1,-1/2 invalid because l > n (violates rule 2)
</span>
<span /><span /><span>viii) 3,3,1,1/2 invalid because l = n (violate rule 2)
</span>
<span /><span /><span>ix) 2,-2,-2,-1/2 invalid because l is negative (violates rule 2)
</span>
x)<span> 3,2,2,1/2 valid: meet the four rules</span>
xi)<span> 4,2,1,1/2 valid: meet the four rules</span>
<span /><span>
</span><span>
</span><span>xii) 2,1,-1,-1/2 valid meet the four rules</span>
Answer:
800mL
Explanation:
Using Boyle's law which states that the volume of a given mass of gas is inversely proportional to the pressure, provided temperature remains constant
P1V1= P2V2
P1 = 2 atm, V1 = 2000mL ,
P2 = 5atm , V2 = ?
2 × 2000 = 5 × V2
Divide both sides by 5
V2 = 4000 ÷ 5
V2 = 800mL
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The notations representing the different isotopes of the element sodium are:
4) 22Na and 23Na
The total number of recognized isotopes of sodium is 20. It starts from 18Na upto 37Na with two isomers (22mNa and 24mNa).
23Na is considered as monoisotopic element meaning it has a single stable isotope making it primordial isotope. 23Na is a single isotope since earth was formed. It has a standard atomic mass of 22.989 769 28(2) u.
22Na, a positron-emitting isotope with a long half life = 2.605 years. It is used to create test objects and point sources for PET or positron emission tomography.