For double-helix formation, change in Gibbs free energy, ΔG, can be measured to be −54 kJ⋅mol^−1 (−13 kcal⋅mol^−1) at pH 7.0 in 1M NaCl at 25 °C ( 298 K). The heat released indicates an enthalpy change, ΔH, of −251 kJ⋅mol−1 (−60 kcal⋅mol^−1). For this process, calculate the entropy change for the system, ΔS system, and the entropy change for the surroundings, ΔS surroundings.

ΔS system =  -661 j/mol.K,  ΔS (surrounding) = 842 j/mol.K

Explanation:

Given that;

ΔG system  = -54 kj/mol = -54000 j/mol

ΔH system = -251 kj/mol = -251000 j/mol

Temperature T = 25 degree Celsius = 298 Kelvin

Now

ΔG system = ΔH system  -  T(in kelvin) * ΔS system

SO WE SUBSTITUTE

-54000 = -251000 - 298 * ΔS system

ΔS system =  -661 j/mol.K

q(surroundings) (heat flow into surroundings) = -q(system) (heat flow into system), and q(system) = -ΔH(system) at constant pressure.

Thus q(surroundings) = -ΔH(system).

now q(surroundings) = -ΔH system = +251000 j/mol

so

ΔS (surrounding) = q(surroundings) / T

ΔS (surrounding) = 251000 / 298

ΔS (surrounding) = 842 j/mol.K

electron microscopy and scanning tunneling microscopes gives us a greater understanding of atoms by being able to see the atom itself, and lets us see some atomic reactions.

explanation:

2fe + 3h2so4 -> fe2(so4)3 + 3h2

it is necessary to balance equations in order to get the proper amount of reactants as well as products in order not to make a miscalculation.

you cannot change the subscripts as that would change the substance itself. for instance, diatomic elements such as h2 only have the subscript two when a gas. another example would be so4, if you were to change the subscript, the element would no longer be sulfate.

we change the coefficients instead as that only changes the number of molecules rather than the substance itself.

hope this !