Which reactions are spontaneous?

i. c2h5oh(l) + 3o2(g) 2co2(g) + 3h2o(l), g = –36.7 kj
ii. 2c6h6(l) + 15o2(g) 12co2(g) + 6h2o(l), g = –6,405 kj
iii. caco3(s) cao(s) + co2(g), g = 13.0 kj
iv. ni(s) + cl2(g) nicl2(s), g = 1,130.28 kj
a.) i and ii
b.) iii and iv
c.) i and iii
d.) ii and iv

The correct answer is option A.

Explanation:

Gibbs's free energy is defined as the energy which is associated to the chemical reaction that can be used to do work. It is represented as "G".

When Gibbs's free energy is negative, the reaction is said to be spontaneous and when Gibbs's free energy is positive, the reaction is said to be non-spontaneous.

From the given options:

Reaction 1 and reaction 2 has negative Gibbs's free energy and hence, is considered as the spontaneous reactions.

Reaction 3 and reaction 4 has positive Gibbs's free energy and hence, is considered as the non-spontaneous reactions.

Therefore, the correct answer is Option A.

assuming that your periodic table has eighteen columns, you should highlight   the four elements in the third column from the left of the table.

neutral atoms of elements after calcium contain d electrons. the energy of d orbitals of a particular main shell lies between the energy of the s and p orbitals of the next main shell. for example, electrons in the have energy higher than those in the orbital while lower than those of the orbital.

by the aufbau principle, electrons fill orbitals one at a time, starting from those of the lowest energy. the orbital is therefore filled right after orbitals and before orbitals.  

potassium has electron configuration and calcium . the s orbital of a main shell holds a maximum of two electrons. the next element would thus have the electron configuration and satisfy the requirements.

a neutral atom of the element contains three electrons on top of the most recent noble gas element. it should thus be placed in the third column of the periodic table. both scandium and yttrium would satisfy the conditions. an aufbau diagram indicates that the 4f orbital is filled before the 5d. however, it appears that exceptions exists for both lanthanum and actinium. neutral atoms of the two d-block elements also demonstrate the and should be highlighted as well.