Chemistry: what is a zeroth-order reaction?

Tutoring chemistry, reaction order is a topic. The tutor mentions the idea of zeroth-order reaction, with an example.

A zeroth-order reaction is one that proceeds at the same rate even if the concentration of reactant is increased. Of course, there must be sufficient reactant for the reaction to happen at its baseline rate. Having met that condition, however, increasing the reactant concentration does not increase the rate of a zeroth-order reaction.

Zeroth-order reaction is not necessarily an intuitive idea, but here’s an example: the liver’s processing ability of alcohol is often described as about an ounce per hour, regardless of how much the person consumes. If true, then the liver’s processing of alcohol is zeroth order: its rate does not increase even if more alcohol (the reactant) is introduced.

Source:

Mortimer, Charles E. Chemistry, sixth edition. Belmont: Wadsworth Publishers, 1986.

UC Santa Cruz

Jack of Oracle Tutoring by Jack and Diane, Campbell River, BC.

Warming ice, melting ice, and cooling water

Tutoring chemistry, heat flow between hot and cold substances might be studied. The tutor mentions a reflection about water and ice.

Today, while thawing chicken breasts in water, I wondered how much water would be needed to supply the necessary heat to thaw them.

Interestingly, solid ice heats up twice as easily as liquid water cools: it takes 2.09kJ/kg to warm ice one degree Celsius (say, for instance, from -4C to -3C), but liquid water releases 4.18kJ/kg for each degree Celsius it cools.

Melting ice is a more demanding proposition: it takes about 160 times as much heat to melt a kilogram of ice as to heat it one degree Celsius (once again, from -4C to -3C, for example). In particular, it takes 334kJ/kg to melt ice.

Source:

Hebden, James. Chemistry: Theory and Problems, Book Two. Toronto: McGraw-Hill Ryerson, 1980.

Jack of Oracle Tutoring by Jack and Diane, Campbell River, BC.

Natural gas vs propane: part 0

Self-tutoring about common fuels: the tutor makes an initial comparison of natural gas to propane.

Natural gas is chiefly methane, CH4; propane is C3H8.

The combustion equation for methane:

CH4 + 2O2 → CO2 + 2H2O

Propane’s combustion equation, on the other hand, is

C3H8 + 5O2 → 3CO2 + 4H2O

Therefore, methane uses 2/5, or 40% as much oxygen as propane to combust; its heat value is about 40% of propane’s as well (38.7 vs 93.2 MJ/m3).

Source:

www.elgas.com.au

www.eia.gov

Jack of Oracle Tutoring by Jack and Diane, Campbell River, BC.

Flash point vs fire point: what is the difference?

Self-tutoring about safe temperature to heat cooking oil led the tutor to seek the difference between flash point and fire point.

At the flash point, the vapor is ignitable but will only burn with a continuous source of ignition. At the fire point, the vapor, once ignited, will burn independently, even if the ignition source is removed.

Source:

www.differencebetween.com

Jack of Oracle Tutoring by Jack and Diane, Campbell River, BC.

Chemistry: acid nomenclature: hypo acids

Tutoring chemistry, naming acids might arise. The tutor brings up a time to use hypo in naming an acid.

From a simple point of view, the hypo acid has one less oxygen than the -ous acid. For example:

chlorous acid: HClO2

hypochlorous acid: HOCl

Source:

Mortimer, Charles E. Chemistry, sixth ed. Belmont: Wadsworth, 1986.

Jack of Oracle Tutoring by Jack and Diane, Campbell River, BC.

Biology: what mineral form of calcium is found in bones?

Tutoring biology, the question about calcium in bone – specifically, which mineral form it takes – might arise. The tutor discusses it.

The hardness of bone comes from the presence of hydroxyapatite:

hydroxyapatite:

Ca5(PO4)3OH

found in bones and giving them their hardness.

Source:

answersingenesis.org

www.iofbonehealth.org

www.fluidnova.com

www.w3schools.com

Jack of Oracle Tutoring by Jack and Diane, Campbell River, BC.

Chemistry: what are degenerate orbitals?

Tutoring chemistry, you sometimes cover bonding. The tutor defines degenerate orbitals.

Degenerate: being two separate objects with a single, identical value.

The 1s orbitals of two separate hydrogen atoms are degenerate because, isolated from each other, they share a single, identical energy level.

When the two hydrogen atoms bond together, their separate 1s orbitals merge into two hybrids, one of high energy, the other low. There are still two orbitals, but each of unique energy level, so the degeneracy is erased.

Such is how I understand degenerate orbitals from the reading:)

Source:

Mortimer, Charles E. Chemistry, 6th ed. Belmont: Wadsworth, 1986.

chemistry.stackexchange.com

Jack of Oracle Tutoring by Jack and Diane, Campbell River, BC.

Chemistry: disproportionation

Tutoring chemistry, you likely touch on redox. The tutor shows a disproportionation.

disproportionation: a reaction in which the same species both oxidizes and reduces.

Example:

Cu+ → Cu2+ + e E=-0.153
Cu+ + e → Cu(s) E=0.521

The above disproportionation, theoretically, is spontaneous, since the potentials (E) sum positive (0.368V in this case).

Source:

Mortimer, Charles E. Chemistry, 6th ed. Belmont: Wadsworth, 1986.

sites.chem.colostate.edu

Jack of Oracle Tutoring by Jack and Diane, Campbell River, BC.

Chemistry: groups IB and IIB

Tutoring chemistry, the periodic table is important. The tutor mentions a peculiarity of it.

The transition metals are the elements in the middle of the periodic table, starting the fourth row from the top. Their first element is scandium (Sc).

On some periodic tables, you’ll notice that scandium (Sc, 21) is under group IIIB, then follows titanium (Ti, 22) under IVB, and so on. However, if you continue across, you’ll notice that copper (Cu, 29) is under IB, then zinc (Zn, 30) is under IIB. Why do IB and IIB appear at the right side, while IIIB appears at the left?

Beginning with scandium, the 3d subshell is being filled, but 4s, in the shell above, already is. Scandium is 3d14s2. At nickel (Ni, 28), the 3d subshell has 8 electrons, the 4s, 2. However, at copper (Cu, 29), the 3d subshell gains two electrons to reach 3d10, while 4s drops to 4s1. Zinc has 3d104s2. Perhaps it’s the refilling of the outer s subshell that defines IB and IIB at the right side of the transition metals.

In the next period, silver (Ag, 47) has 5s1, while cadmium (Cd, 48) has 5s2. However, the filling of 4d happened back at palladium (Pd, 46).

One more period down, gold (Au, 79) has 6s1, while mercury (Hg, 80) has 6s2.

Source:

Mortimer, Charles E. Chemistry, 6th ed. Belmont: Wadsworth, 1986.

Jack of Oracle Tutoring by Jack and Diane, Campbell River, BC.

Physics, chemistry: closed system vs isolated system

Tutoring physics or chemistry, definitions are always important. The tutor compares closed system with isolated system.

A closed system cannot lose or gain matter; it cannot exchange matter with the surrounding environment.

An isolated system is closed as above, but also with regards to energy. That is to say, an isolated system cannot exchange matter or energy with the surrounding environment.

Source:

Giancoli, Douglas C. Physics, 5th ed. New Jersey: Prentice Hall, 1998.

Jack of Oracle Tutoring by Jack and Diane, Campbell River, BC.