Answer:
c) the attraction of an atom for the electrons in a covalent bond.
Explanation:
Electronegativity, symbol χ, is a chemical property describing an atom's ability of to attract a shared pair of electrons to itself. It is influenced by the atomic number of the atom and the distance between the valence electrons and the charged nucleus. As the electronegativity number of atoms increases, the more the atom attracts electrons towards itself.
Answer:
The answer is option 3, C5H12 + 8O2 → 5CO2 + 6H2O.
Explanation:
In an exothermic reaction, the energy change(ΔH) will always be a negative value.
For endothermic reaction, the energy change's value is positive.
In the options above, option 1 and 2 are endothermic reaction.
Answer:
0.17%
Explanation:
With the equation:
2Cr2O7 2- + C2H5OH + H2O --> 4Cr3+ + 2CO2 + 11H2O
We can assume that every mole of ethanol needs 2 moles of Dichromate to react.
So if in 1L we have 0.05961 moles of dichromate we can discover how many moles we have in 35.46mL
1000 mL - 0.05962 moles
35.46 mL - x
x = 
x = 2,11* 10^-3 moles
As we said earlier, 1 mole of ethanol needs 2 mole of dichromate, so in the solution we have 1,055*10^-3 moles of ethanol. We can discover the mass of ethanol present in the solution.
1 mole - 46g
1.055*10^-3 - y
y = 46 * 1.055*10^-3
y = 0.048 g
To discover the percent of alchol we can use a simple relation
28 g - 100%
0.048 - z
z = 
z = 0.17%
For a closed system, you need two things:
1) a conservation of mass within the boundaries of the system
2) the ability to freely exchange energy to & from the "closed" system with a surrounding external system
So, the answer is <u><em>never</em></u>, since your defining the "system" as the water within the bathtub, and an open bathtub is exposed to evaporation, which is not conserving mass within the defined "system".
