1. Scientists before Mendeleev had observed that certain elements reacted similarly with other chemicals. Which further observation led Mendeleev to create the periodic table?
A The elements within these groups often differed
physical properties, such as color and texture
B. The atomic weights of the elements within these groups were spaced at nearly regular increments
C The reactivity of the elements within these groups varied at nearty regular increments
D. Elements that did not fit in these groups belonged in the lanthanide and actinide series
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B The atomic weights of the elements within these groups were spaced at nearly regular increments

"standard molar enthalpy:

h2o ( liquid water ) : - 285.8 kj/mole

h2o ( water vapor ) : - 241.8 kj / mole.

δhrxn = - 241. 8 - ( - 285.8 )= -241.8 + 285.8 = 44.0

answer: 44.0 kj"

the best answer is d because the strong cohesion is caused by the ability of water molecules to undergo hydrogen bonding.

a is incorrect because when water solidifies, it becomes   ice, which expands and occupies a bigger volume for the same mass of water in its liquid state.

b is incorrect because water has high surface tension. besides bonding to itself it hydrogen bonds to other molecules at the top decreasing possibility for breaking of attractive forces.

c is incorrect because the water molecule has oxygen which is highly electronegative and so pulls the electron pair towards itself creating a dipole moment, making the molecule polar.

e is incorrect because water has strong adhesion, ability to stick to other molecules such as glass because of this molecules having stronger hydrogen bonding than water.