<span>The state of the helium in its natural form is gaseous and is a chemical element of colorless aspect and belongs to the group of noble gases. The atomic number of helium is 2. The chemical symbol of helium is He. For the following we focus on those elements and relate it with similar chemical properties. Then we find that; Neon, Hydrogen, Boron and Carbon are related to helium, either by proximity in their atomic number or period or by their group.</span>
Answer:
Determining the pH of substances such as purple grape juice and catsup using test strips can be difficult. Why?
Explanation:
Due to the tartaric acid present in these substances, this is a weak acid and is the predominant type of acid in grapes.
pH meters for these substances, measure the total acidity of the sample and convert it into tartaric acid concentration; The test strips are a qualitative method of measurement and their result can give different opinions.
Answer:
∆H° rxn = - 93 kJ
Explanation:
Recall that a change in standard in enthalpy, ∆H°, can be calculated from the inventory of the energies, H, of the bonds broken minus bonds formed (H according to Hess Law.
We need to find in an appropiate reference table the bond energies for all the species in the reactions and then compute the result.
N₂ (g) + 3H₂ (g) ⇒ 2NH₃ (g)
1 N≡N = 1(945 kJ/mol) 3 H-H = 3 (432 kJ/mol) 6 N-H = 6 ( 389 kJ/mol)
∆H° rxn = ∑ H bonds broken - ∑ H bonds formed
∆H° rxn = [ 1(945 kJ) + 3 (432 kJ) ] - [ 6 (389 k J]
∆H° rxn = 2,241 kJ -2334 kJ = -93 kJ
be careful when reading values from the reference table since you will find listed N-N bond energy (single bond), but we have instead a triple bond, N≡N, we have to use this one .
