According to glassware manufacturing specifications, volumetric pipets are supposed to deliver the amount stamped on the pipet to /- 0.02 mL, graduated cylinders are supposed to be able to make deliveries good to /- 0.1 mL, and the volume measurements on beakers are supposed to be used only as approximations. The degree of care that goes into making each of these pieces of glassware differs considerably, as evidenced by their relative price. A 50 mL volumetric pipet, graduated cylinder and beaker have a list price in the Fisher Scientific catalog of $21.06, $8.02, and $3.95, respectively. A student performed the experiment you performed in class using a beaker and a graduated cylinder in place of the volumetric pipet. She tentatively reported each resulting density to 4 sig figs, to better see what kind of reproducibility she would obtain. Correlate each data set to each piece of glassware.

Beaker
Graduated cylinder
Volumetric pipet

a. 1.206 g/mL, 1.033 g/mL, 1.345 g/mL
b. 1.136 g/mL, 1.140 g/mL, 1.128 g/mL
c.1.170 g/mL, 1.171 g/mL, 1.168 g/mL

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 correct answer is b. a strong acid completely dissociates to its ions when dissolved in water. completely dissociates to and ions. a is incorrect because does not fully ionize to and ions and some remain as the compound . c and d are incorrect because, and do not fall into the category of bronsted lowry acids. a bronsted lowry acid is a proton donor and since both molecules do not have a proton to donate they are not bronsted lowry acids. likewise,   if we use the lewis acid definition, they cannot be acids. a lewis acid is an electron pair acceptor. both and have a complete octet so can not accept any electrons which disqualifies them as acids.