At a certain temperature, the equilibrium constant, , for this reaction is 53.3. h2(g)+i2(g)↽−−⇀2hi(=53.3 at this temperature, 0.500 mol h2 and 0.500 mol i2 were placed in a 1.00 l container to react. what concentration of hi is present at equilibrium?

[HI]=0.785 M

Explanation:

Kc=53.3

First, write the equation of the equilibrium constant:

This equation is the only one that we will need to solve the problem, but thinking on a new variable; let's call the variable 'x' and it will mean: moles of H2 that reacts (or moles of I2 that react, the result will be the same). If x moles of H2 reacts, the molar change will be x M (because the volume is 1 liter), so the molar concentration of each compound will be:

The last was written having in mind the stoichiometry of the reaction; The subscript  zero means the initial concentration, which is zero for the case of HI, and 0.5 for I2 and H2. Let's replace these equations in the equilibrium constant equation:

The only unknown from this is 'x', so let's solve the equation:

Two roots are obtained, but x=0.6886 does not have sense, because we just put 0.5 M on the container, it is impossible that more than that reacts.

So, x=0.3925 M.

And the equilibriums concentrations can be calculated:

[HI]=2*x=0.785 M

[H2]=[I2]=0.5-X=0.1075 M

You can replace that concentrations on the equilibrium constant equation, and you will see that it gives the constant 53.3 as a result.

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.”

the atomic number will stay the same no matter how many electrons it has, so it doesn’t decrease nor increase. it’ll only change with a different number of protons