Answer: Cobalt, because it is an element that is not bonded together with anything else.
(2) U-238 is the radioisotope used in dating geological formations. Uranium-238 has a half-life of 4.46 billion years, which makes it suitable to date such old formations.
The other options do not have such long durabilities and half-lives.
Answer:
1) 40
2) 2.25 moles
3) 17
4) 120
5) Fe₂O₃
Explanation:
Please see attached picture for full solution.
The standard formation equation for glucose C6H12O6(s) that corresponds to the standard enthalpy of formation or enthalpy change ΔH°f = -1273.3 kJ/mol is
C(s) + H2(g) + O2(g) → C6H12O6(s)
and the balanced chemical equation is
6C(s) + 6H2(g) + 3O2(g) → C6H12O6(s)
Using the equation for the standard enthalpy change of formation
ΔHoreaction = ∑ΔHof(products)−∑ΔHof(Reactants)
ΔHoreaction = ΔHfo[C6H12O6(s)] - {ΔHfo[C(s, graphite) + ΔHfo[H2(g)] + ΔHfo[O2(g)]}
C(s), H2(g), and O2(g) each have a standard enthalpy of formation equal to 0 since they are in their most stable forms:
ΔHoreaction = [1*-1273.3] - [(6*0) + (6*0) + (3*0)]
= -1273.3 - (0 + 0 + 0)
= -1273.3
This thermochemical equation needs to be balanced. Hence, option B is correct.
<h3>What is a balanced chemical equation?</h3>
A balanced equation contains the same number of each type of atom on both the left and right sides of the reaction arrow.
The balanced thermochemical equation is:
→ 
Hence, option B is correct.
Learn more about the balanced chemical equation here:
brainly.com/question/8062886
#SPJ1
