Answer:
There are lots of methods.
Explanation:
Usually, animals like pandas live a shorter lifespan in the wild than in captivity. A little fact, there is only one brown panda in the entire world, so it would be very, very rare to see one. The Smithsonian National Zoo, for example, are working to protect pandas, as well as other species.
Answer:
-125 kJ
Explanation:
You calculate the energy required to break all the bonds in the reactants. Then you subtract the energy to break all the bonds in the products.
H₂C=CH₂ + H₂ ⟶ H₃C-CH₃
Bonds: 4C-H + 1C=C 1H-H 6C-H + 1C-C
D/kJ·mol⁻¹: 413 612 436 413 347
The formula relating ΔHrxn and bond dissociation energies (D) is
ΔHrxn = Σ(Dreactants) – Σ(Dproducts)
(Note: This is an exception to the rule. All other thermochemical reactions are “products – reactants”. With bond energies, it’s “reactants – products”. The reason comes from the way we define bond energies.)
<em>For the reactant</em>s:
Σ(Dreactants) = 4 × 413 + 1 × 612 + 1 × 436 = 2700 kJ
<em>For the products:</em>
Σ(Dproducts) = 6 × 413 + 1 × 347 = 2825 kJ
<em>For the system</em>
:
ΔHrxn = 2700 - 2825 = -125 kJ
B, the opposing forces are the same, thus, the ball doesn't move back or forward.
The quantity of NaOH required to reach the third equivalence point is 20mL.
Using the titration formula,
CaVa/CbVb = Na/Nb
Where,
Ca = concentration of citric acid (0.200 M)
Cb = concentration of NaOH (0.750 M)
Va = Volume of citric acid (25.0 mL)
Vb = volume of NaOH (x mL)
Na = number of reacting mole of citric acid (3)
Nb = number of reacting mole of NaOH (1)
Therefore Vb ( x mL) =CaVaNb/CbNa
= 0.2× 25×3/0.75 ×1
= 15/0.75
Vb ( x mL) = 20 mL
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