Let's react! Trivia Quiz

Answer: H2O

It's easy to forget, but burning hydrocarbons, alcohols and carbohydrates does not only release carbon dioxide but also water. The complete reaction is

2 CH3OH + 3 O2 = 2 CO2 + 4 H2O.

Answer: NaCl

A good (but not foolproof) way to remember the outcome of a neutralization is "acid plus base gives salt plus water". Strictly, this is only true in an aqueous solution, however, where the actual reaction consists of a proton transfer from a H3O+ ion to an OH- one. The ions making up the salt don't actually take part in the reaction at all, but they are left over once the water evaporates.

HCl + NaOH = NaCl + H2O.

Answer: CaSO4

Out of the four cation-anion combinations given in this experiment, CaSO4 is the only one poorly soluble in water, so it will immediately precipitate once the two original solutions are mixed. CaSO4 is also known as gypsum.

Na2SO4(aq) + CaCl2 (aq) = 2 NaCl (aq) + CaSO4 (s).

Answer: CO2

Fermentation is a way for organisms to generate energy out of glucose without needing oxygen. Ethanol fermentation is a very common type, with most of the energy release being caused by the formation of the very stable CO2 (the ethanol still contains a lot of energy).

C6H12O6 = 2 C2H5OH + 2 CO2.

Answer: C2H4F2

Was that easy? I hope so. Additions yield only one product which is the combination of the two (or more) reactants. Halogens readily add onto a double bond such as that in ethene.

C2H4 + F2 = C2H4F2.

You could also write the product as a condensed formula to show that each of the carbon atoms bonds with one of the fluorines: CH2F-CH2F.

Answer: H2

Yes, that gas is pure hydrogen which can then be burnt in a second step to add a spectacular fireball to the already impressive display. The underlying reaction is a redox one - potassium is oxidized to K+ while the oxygen from water is reduced to oxide (O--), releasing the two hydrogen atoms it was bonded to. The fresh oxide ion further then reacts with another water molecule to make two hydroxide ions (OH-).

2 K + 2 H2O = H2 + 2 KOH.

Answer: N2O

We can split two water molecules (four hydrogen and two oxygen atoms) from the original salt and be left with two nitrogen and one oxygen atom. These combine to form nitrous oxide, also known as laughing gas.

NH4NO3 = 2 H2O + N2O.

Answer: Fe2O3

Iron readily forms three different oxides: Ferrous oxide or wüstite (FeO), magnetite (Fe3O4) and ferric oxide, hematite or rust (Fe2O3). Fe2O3 as hematite is by itself a well-defined crystalline mineral and an important iron ore. Its interaction with water is what creates the red, flaky form we know as rust.

4 Fe + 3 O2 = 2 Fe2O3.

Answer: H2SO4

The process I mentioned is indeed not only the laboratory process but also the industrial way of obtaining the important sulfuric acid. Sulfur is readily available as an unwanted trace component in fossil fuels, from which it needs to be removed as its oxides are toxic and harm the environment. Controlled burning of this sulfur in the presence of vanadium gives us sulfur trioxide, SO3, which is then further reacted with water to yield the desired H2SO4.

S8 + 12 O2 = 8 SO3 (or H2S + 2 O2 = H2O + SO3), followed by
SO3 + H2O = H2SO4.

Answer: Ag

In spite of their black appearance, these crystals are actually pure silver. This color is due to the crystals' surface not being smooth but rather fractal in shape. The blue color of the solution results from copper ions (Cu+).

AgNO3 + Cu = CuNO3 + Ag.

The reason for this reaction is that silver is the nobler metal, so when silver ions dome into contact with elemental copper, they attract an electron from it. The copper ion enters the solution while the silver precipitates on the surface of the copper. As both silver and copper are excellent electric conductors, this electron transfer can even happen when the silver ions only contact already present silver, leading to the hairlike crystal growths instead of a smooth silver plating.