The molar mass of Na₂SO₄ -
2 x Na - 2 x23 = 46
1 x S - 1 x 32 = 32
4 x O - 4 x 16 = 64
total = 46 + 32 + 64 = 142 g/mol
the molarity of solution - 2.0 M
in 1 L of solution , 2.0 moles
Therefore in 2.5 L - 2 mol/L x 2.5 L = 5 mol
then the mass of Na₂SO₄ required = 142 g/mol x 5 mol = 710 g
The molecular basis of the property of water responsible for the presence of ice on the surface of a frozen lake is Solid-phase water—ice—has an extraordinary property
Water has extremely strong hydrogen bonds with itself, which accounts for its high boiling and freezing points. However, in the liquid state, the arrangement of the molecules and hydrogen bonds is arbitrary. Because of the two oxygen lone pairs and the water's 104.5-degree H-O-H bond angle, the more structured array that forms when the molecules freeze places them farther apart than the random liquid. The resulting solid has a lower density because the molecules are more spaced apart than in a liquid.
Ice, a solid form of water, has the remarkable feature of being less dense than liquid water. Almost exclusively only water has a solid phase that floats on a liquid. Lakes and rivers are protected from the subzero winter air by frozen, floating water, which keeps them liquid and able to support life.
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5 because the protons determine the atomic number
30.
30+5=35
35/7=5.
5+12= 17.
17-7=10
