I've been trying to work out which of the following make best grammatical sense but have been looking at them for so long now that my mind has turned to mush and they both seem wrong.

Which is better form:

A total of 0.0605 moles (3 s.f.) of NaOH was originally added to the aspirin


A total of 0.0605 moles (3 s.f.) of NaOH were originally added to the aspirin

I know that moles is plural but personally I think was is the better of the two. I would appreciate some opinions on which reads better to people.

  • Your instinct was right. It is was. See my comment at Armen Tsirunyan.
    – Kris
    Feb 19, 2012 at 13:26
  • 1
    This is not a duplicate of Should we use plural or singular for a fraction of a mile?. This question is about subject/verb agreement, it's not about the plurality of the measure itself, which is what that question answers. It's also not about 'a total of', which is a red herring here.
    – Alan Munn
    Feb 19, 2012 at 13:36
  • @Kris: I have deleted my answer as it was wrong so you'd better repost your comment here again :) Feb 19, 2012 at 13:42
  • @ArmenTsirunyan How on earth (and where from) would I 'repost my comment' after your deleting it? lol.
    – Kris
    Feb 19, 2012 at 13:58
  • @Kris: I had forgotten that you needed 10K rep to view deleted posts. Your comment is: "0.0605 moles (3 s.f.) of NaOH was originally added to the aspirin." -- it would still be was, because you do not add a mole at a time or by counting the moles as such. Take ten teaspoonfuls of water and add it, not them, to the mix. Feb 19, 2012 at 14:07

2 Answers 2


When referring to amounts of objects as opposed to the objects themselves, you normally use singular agreement. This has nothing to do with fractional amounts, and nothing to do with the use of 'a total of', but is a property of amounts in general.

  • 40 litres of water was/*were poured into the tank.
  • (A total of) 0.0605 moles (3 s.f.) of NaOH was/*were originally added to the aspirin.

We can see this when use anaphora to refer to the amount.

  • 40 litres of water was poured into the tank. It/*They filled it to the brim.
  • John weighs 200lbs. It is too much for his height./*They are too much for his height.

As TimLymington points out in the comments, there are some interesting wrinkles in this, although they simply confirm the statement above. Fractions always control plural number within the noun phrase, but whether that noun phrase will control plural verbal agreement depends on whether it refers to a measure or the objects themselves. So in the example below, plural agreement is used (not singular) because the noun phrase "0.5 apples" refers to actual apples and not to a measure.

  • 0.5 apples were added to the mixture.

We can see this more clearly with the following examples, which don't use fractions.

  • 30 lbs of potatoes were/?was peeled for the banquet.
  • 30 lbs of potatoes is/*are not enough to feed this crowd.

In the first example, we are referring to the actual potatoes, and so the agreement is plural. Singular is marginally possible if we are referring to the measure. In the second example we are referring to the measure, and agreement is singular.

  • 1
    Fascinating. I agree with the different agreement needed in your last two examples. Expanding gives something like the more felicitous but clumsier and less idiomatic: 'Potatoes whose combined weight was 30 lb were peeled for the banquet.' and '30 lb of potatoes is not a large enough ration to feed this crowd.'. Jul 31, 2017 at 22:32

In case any other scientist consults this page he should be reminded that according to the standard SI units of nomenclature, which all reputable modern scientific journals follow:

  1. Units are not written in full, but abbreviated.

  2. Unit symbols are unaltered in the plural

Thus, the English Scientific Usage is:

A total of 0.0605 mol of NaOH was originally added to the aspirin


A total of 6.05 mol of NaOH was originally added to the aspirin

(The abbreviation for ‘mole’ being ‘mol’)

As explained in the accepted answer, the verb is in the singular in any case.

Examples are not easy to find just by surfing because of the scientific style of writing in the passive and naming the constituent with the amount following in parentheses, but here is one from the respected US journal, Biochemistry (vol 14, p.4828, 1975):

“To 0.6 ml of vesicle solution was added 0.2 ml of 1.6% Triton…”

(‘ml’ is the abbreviation for ‘millilitre’)

  • Old news, but I thought I should add this for completeness and include an actual example. The reason for choosing a paper that is over 40 years old is because this level of detail is usually relegated to online supplementary material today, and are less accessible to surfing. (Also sub-editing to house style ain‘t what it used to be.)
    – David
    Jul 31, 2017 at 15:45

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