Astudent weights out 635.94 g na2co3 and dissolved it in 2.0 l water. what is the molarity of his solution?

You have to find out the number of moles of the substance.

I will use rounded numbers for the atomic weights because every periodic table is different.

2Ca = 2 * 40 =  80

1 C   = 1 * 12  =   12

3O = 3  * 16  =   48

Atomic Mass = 140

moles = given mass / molar mass

moles = 635.94 / 140

moles = 4.54

Now you need to find the concentration

C = moles / Volume in liters.

C = 4.54/ 2.0 L

C = 2.27 moles / L

Technically since the volume is only 2 significant digits, your answer should be 2.3 moles / L

If you do not have this as a choice, what are your choices.

solute : a solute is a substance that is dissolved in another substance is known as a solvent. it is mixed with a special mixture know as homogeneous mixture.

solvent: a solvent is a substance that dissolved a solute, which results in a solution is known as solvent.

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.