Determine the empirical formula for a compound that has the following analysis: 8.09% carbon, 0.34% hydrogen, 10.78% oxygen, and 80.78% bromine.

C₂HO₂Br₃

Explanation:

Data given

Carbon = 8.09%

Hydrogen = 0.34%

Oxygen = 10.78%

bromine = 80.78%

Empirical formula = ?

Solution:

First find the masses of each component

Consider total compound is 100g

As we now

mass of element = % of component

So,

8.09 g of C = 8.09% of Carbon

0.34 g og H = 0.34% of  Hydrogen

10.78 g of O =  10.78% of Oxygen

80.78 g of bromine = 80.78% of bromine

Now convert the masses to moles

For Carbon

Molar mass of C = 12 g/mol

            no. of mole = mass in g / molar mass

Put value in above formula

            no. of mole = 8.09 g/ 12 g/mol

            no. of mole = 0.674

mole of C = 0.6742

For Hydrogen

Molar mass of H = 1 g/mol

              no. of mole = mass in g / molar mass

Put value in above formula

              no. of mole = 0.34 g/ 1 g/mol

               no. of mole = 0.34

mole of H = 0.34 mole

For Oxygen

Molar mass of O = 16 g/mol

              no. of mole = mass in g / molar mass

Put value in above formula

              no. of mole = 10.78 g/ 16 g/mol

               no. of mole = 0.674

mole of O = 0.674 mole

For Br

Molar mass of Br = 80 g/mol

             no. of mole = mass in g / molar mass

Put value in above formula

              no. of mole = 80.78 g/ 80 g/mol

              no. of mole = 1.0098

mole of Br = 1.0098 moles

Now we have values in moles as below

C = 0.6742

H = 0.34

O = 0.674

Br = 1.0098

Divide the all values on the smallest values to get whole number ratio

C = 0.6742 / 0.34 = 1.983 ≅ 2

H = 0.34 / 0.34 = 1

O = 0.674 /0.34 = 1.983 ≅ 2

Br = 1.0098 / 0.34 = 2.97 ≅ 3

So all have round value 1 mole

C = 2

H = 1

O = 2

Br = 3

So the empirical formula will be C₂HO₂Br₃ i.e. all 3 atoms in simplest small ratio

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.”