C) It determines the concentration of an unknown substance in neutralization reactions.
Answer:

Explanation:
Hello,
In this case, since the density is defined as the ratio between the mass and the volume as shown below:

We can compute the density of water for the given 43 g that occupy the volume of 43 mL:

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Mendeleev arranged the elements according to their atomic masses
Answer:
they are producers and they have means to keep themselves warm
Explanation:
I took test and saw answer.
Even though Hydrogen is originally in group 1, based on this property, we can say it is in group 6.
Because:
Group 6 would mean that it only needs 2 more valence electrons till the octet (8 valence electrons). This would make it reactive, yet, in normal conditions, unlike group 7.