The density of the sample is:
Density = mass / volume
Density = 9.85 / 0.675
Density = 14.6 g/cm³
If the sample has 95% gold, and 5% silver, its density should be:
0.95 x 19.3 + 0.05 x 10.5
Theoretical density = 18.9 g/cm³
The difference in theoretical and actual densities is very large, making it likely that the jeweler was not telling the truth.
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
Answer : The moles of 
are, 2.125 mole.
Explanation : Given,
Molarity of = 8.500 M
Volume of solution = 250 mL = 0.250 L (1 L = 1000 mL)
Molarity : It is defined as the number of moles of solute present in one liter of volume of solution.
Formula used :
Now put all the given values in this formula, we get:
Therefore, the moles of are, 2.125 mole.
Answer:
Constraints are restrictions that need to be placed upon variables
Explanation:
Constraints are restrictions (limitations, boundaries) that need to be placed upon variables used in equations that model real-world situations. It is possible that certain solutions which make an equation true mathematically, may not make any sense in the context of a real-world word problem.
Answer:
–500KJ
Explanation:
Data obtained from the question include the following:
Heat of reactant (Hr) = 800KJ
Heat of product (Hp) = 300KJ
Enthalphy change (ΔH) =..?
The enthalphy change is simply defined as the difference between the heat of product and the heat of reactant i.e
Enthalphy change = Heat of product – Heat of reactant
ΔH = Hp – Hr
With the above formula, we can easily calculate the enthalphy change as follow
ΔH = Hp – Hr
ΔH = 300 – 800
ΔH = –500KJ.
Therefore, the overall energy change for the reaction between hydrogen and oxygen shown in the diagram above is –500KJ
