Heavy water, D2O (molar mass 20.03) can be separated from ordinary water by the difference in the relative rates of diffusion of the molecules in the gas phase. Calculate the relative rate of diffusion of H2O to D2O. (Atomic weights: O

1.58

Explanation:

This problem can be solved by using a law that was proposes in the year 1848, the law is known as the Graham's law of effusion. The law shows the relationship between square root of the density of a particular gas and the rates of effusion. The Graham' s law can be represented mathematically by using the formula below;

(NOTE: the question asked us to Calculate the relative rate of diffusion of H2O to D2O).

==> Rate of H2O effusion/ rate of D2O effusion = √ ( M{D2O} / M{H2O} ).

Also, we should know that Graham's law shows the relationship between the square root of density and the rate of effusion it can also show the relationship between the square root of the molar mass and the rate of effusion.

So, by using the Graham's law formula we will have;

Rate of H2O effusion/ rate of D2O effusion = √ ( M{D2O} / M{H2O} ). Where the molar mass of H2O = 18 gmol^- and D2O molar mass = 20 grams per mole.

Rate of H2O effusion/ rate of D2O effusion = √ (20/ 18).

Rate of H2O effusion/ rate of D2O effusion = √ 2.5.

Rate of H2O effusion/ rate of D2O effusion = 1.58.

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pre-sliced bread is a relatively recent development in baking technology. previous to that, it was always sold in a bakery in daily-made contiguous loaves with no wrapping, and was moderately perishable, usually being used with a day or two (which is why every bakery had a discounted “day-old” bread table.) therefore, pre-sliced bread would grow stale quickly. the hard crust provided a protective layer, and once the exposed dry slice left from the previous cut was removed, the interior was still soft.

what keeps bread soft is the moisture retained in the crumb (the light spongy part that’s not crust). the reason the crust develops is the surface of the dough gets exposed to hot dry air during baking which browns the outer layer and seals it, preventing all the moisture from escaping the dough. longer exposure to air will also eventually cause your bread to lose flavor and become stale.

people were used to cutting slices as they needed them and storing bread in a specially-made wooden or metal breadbox or pail with a lid to preserve it longer, but the first automatically sliced commercial loaves were produced on july 6, 1928, in chillicothe, missouri, using a machine invented by otto rohwedder, an iowa-born, missouri-based jeweler.[1] pre-sliced bread would indeed dry out, were it not for another 20th century technology: the plastic bag. bread could now be pre-sliced, and if the enclosing bag remains sealed as much as possible, the bread will remain soft and fresh for longer than if sitting unwrapped on a shelf or enclosed in a bread box that is not air-tight. sealed packaging meant bread could also be sold on store shelves and eliminate frequent trips to a bakery.

sealing bread in a plastic bag had another effect: the moisture in the loaf will re-distribute into the crust and soften it, which is sometimes more pleasing in a sandwich - especially for children whose teeth might not yet be strong enough to tear through a hard crust. a homemade loaf of bread can be sealed in a bag overnight and the crust will become soft like store-bought sandwich bread.

these were novel changes in how bread was produced and sold, which led to the coining of the phrase “the greatest thing since sliced bread.”

they are made of gases.

they have a spherical shape.

they make energy through fusion.