In order to ensure that chemical reaction in the lab behave as

Would it be safe to assume that just as GMAT doesn't prefer 'being', it doesn't prefer 'instead of'.

The question is about what is being compared?
First 3 answers are the same, and they don't compare location to the location.
You need some preposition to say that the heat is applied to some location.
So correct is D

As you can see from this problem, it is critical to determine precisely what is being compared. What is being compared in this sentence? \(Where\) the heat is being applied. If you said “location,” you’re partially correct, but with a significant piece missing. In the first portion of the comparison, the heat is being applied “over the total surface area.” Yes, “the total surface area” is the location of the application, but the word “over” is just as important.

Without a preposition to introduce the location in the second portion of the comparison (“to a series of irregular points”), the comparison lacks equivalency of form. To be properly compared, the heat must be applied evenly:

1. over the entire surface area

rather than

2. to a series of irregular points.

None of the other answer choices (except answer choice E, which is clearly wrong because of the poor diction (“as against being”) contain the necessary preposition of location to make an exact comparison between the same things: where the heat is being applied. The correct answer choice is D.

Please go through this post: https://www.manhattanprep.com/gmat/forums/rather-than-accept-the-conventional-wisdom-that-the-earth-t1177.html
It explains that RAHER THAN is a conjunction and hence can be followed by anything but INSTEAD OF is a complex preposition which should be followed by a noun. The noun can be a gerund as well.

With this, use of INSTEAD OF could be correct if we had the sentence as:

it is important the heat be applied evenly over the total surface area of the flask instead of applying it to a series of irregular points on the surface.

Another post for reference : https://gmat-grammar.blogspot.in/2006/06/rather-than-vs-instead-of.html

Thanks RD.

But, as you explained, instead of is used for noun

I take milk instead of coffee in the breakfast-- correct used for noun

In order to ensure that chemical reaction in the lab behave as predicted by their mathematical formulas, it is important the heat be applied evenly over the total surface area of the flask instead of a series of irregular points on the surface.

both "total surface area" and "a series of irregular points on the surface" are nouns, so we should be allowed to use "instead of" in this case. Did I misunderstand anything ? Please help !

If you use "instead of", the parallelsim must be between two noun phrases (as you correctly identified):

1. the total surface area of the flask
AND
2. a series of irregular points on the surface

The preposition "over" then covers both the above noun phrases. However the usage "OVER a series of points..." is idiomatically incorrect. The correct usage is "TO a series of points....." (Correct usage: over a surface, to a point). Thus the parallelsim should be made between two prepositional phrases:

1. over the total surface area of the flask
AND
2. to a series of irregular points on the surface

Thus use of "rather than" becomes mandatory.

Dear sayantanc2k, I believe the correct phrasal verb that used for the comparison shall be apply sth to sth.

You may refer the screenshot from Cambridge Dictionary.

In order to ensure that chemical reaction in the lab behave as predicted by their mathematical formulas, it is important the heat be applied evenly over the total surface area of the flask instead of a series of irregular points on the surface.
A) instead of
-- apply heat over x instead of y. -- this is incorrect. Also "instead" is used when we substitute. It will be good to use rather.
B) as compared with
-- this is not a correct idiom - "as compared to" is correct. Even after this correction, we will have comparison error as A.
C) in contrast with
-- comparison error as A.
D) rather than to
-- Correct Answer.
E) as against being at
-- illogical.

Dear AnthonyRitz AjiteshArun GMATGuruNY DmitryFarber IanStewart MartyTargetTestPrep VeritasPrepBrian,

Is "OVER a series of points..." a correct idiom in this sentence?
I thought OVER can be the common or starting word for the parallelism.

I hate idiom issues, and they're not what the GMAT is about. Let's not speak of them.

There's nothing inherently wrong with "over a series of points." However, it's quite illogical here, when the preceding phrase is "applied evenly over..."; one certainly does not mean to imply that heat is applied "evenly over a series of irregular points" -- nonsense! See, if you imply the word "over" you get everything that comes with it. That's the problem. Substituting "to" gives you a chance to line up directly after "applied":

"applied"
"(1) evenly over ..."
[versus]
"(2) to..."

Furthermore, implying the preposition more generally creates ambiguity, since it's not entirely clear what "a series of irregular points" is supposed to match up with. It might pick up after "over" and parallel "the total surface area of the flask," but it might also follow "be" or even parallel "the heat" -- illogical, certainly, but also too much work on the reader to have to figure out. Beyond the above-discussed logic issue, adding the preposition "to" simply provides a great deal more structure and therefore clarity to the parallel element in this sentence.

Note: Correct Idiom : X rather than Y <==> (used to compare verbs)
Correct Idiom : X instead of Y <==> (used to compare nouns)

(A) instead of ==> incorrect we are comparing verbs here heat be applied evenly over ..... a series of irregular points on the surface.
(B) as compared with ==> Wrong comparison idiom
(C) in contrast with ==> Wrong comparison idiom
(D) rather than to ==> Correct comparing the verbs heat be applied evenly over ..... a series of irregular points on the surface.
(E) as against being at ==> Wrong comparison idiom

Hence (D)

Kudos are appreciated, If you liked my post

In order to ensure that chemical reaction in the lab behave as predicted by their mathematical formulas, it is important the heat be applied evenly over the total surface area of the flask instead of a series of irregular points on the surface.

(A) instead of
(B) as compared with
(C) in contrast with
(D) rather than to
(E) as against being at

as it is a preference rather thana substitution we have to use rather than to.
so ans is D