It's something to do with the weathering process.
Eg. At night it's really cold, and in the day it's really hot.
Because the temperature keeps changing dramatically day in and day out,
the sand dunes start to be sort of hacked or re-shaped, or even formed.
<span>The correct answers are A, B, and D. The ΔHrxn is equal to the ΔHf when the ΔHf of the reactants is zero, and this can only occur when the reactants are pure elements (not compounds) in their natural phase at ambient temperature.
c) Chlorine's natural phase is gaseous, but since it is a liquid in this reaction, ΔHf ≠ 0.
e) CO is a compound, not a pure element.
f) BaCO3 is a compound, not a pure element.</span>
Answer:
(a) C5H8O2
(b) C2H2Cl2
(c) CH2
(d) CH
Explanation:
We need to find the proportion of the atoms in whole numbers. Given the percentages we can calculate the number of moles and find their proportions.
Assume 100 g and given the atomic weights the moles are calculated.
(a) C = 59.9/ 12.01 = 4.98 ≈ 5.00
H = 8.06/1.007 = 8.00
O = 32/15.999 = 2.00
C5H8O2
(b) C= 24.8/12.01 = 2.06≈ 2.00
H = 2.0/1.007 = 1.99 ≈ 2.00
Cl = 73.1/ 35.453 = 2.06 ≈ 2.00
C2H2Cl2
(c) C = 86/12.01 = 7.16
H= 14/1.007 = 13.90
7.16:13.90 ≈ 1:2
CH2
(d) C = 92.30/12.01 = 7.68
H = 7.7 / 1.007 = 7.65
7.68:7.65 ≈ 1:1
CH
Answer:
ΔH3 = 1/2 (629) - ΔH^0
Explanation:
Given data:
Bond energy of H2 = ΔH1 = 436 Kj/mol
Bond energy of Br2 = ΔH2 = 193 Kj/mol
To find:
Let bond energy of HBr = ΔH3 = ?
Equation:
H2 + Br2 → 2HBr
enthalpy of formation of HBr = ΔH1 + ΔH3 - 2(ΔH3)
ΔH^0 = 436 + 193 - 2(ΔH3)
(436 + 193) - ΔH^0 = 2(ΔH3)
ΔH3 = 1/2 (629) - ΔH^0
False
Phase changes are physical changes and can be easily reverted by adjusting pressure or temperature.
