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You leave in your fridge a glass bottle filled with water and well closed. After some hours you come to take the bottle out of the fridge. Surprise: the bottle has broken into pieces of ice and glass. Question: How do you explain that?

You are given two aqueous solutions A and B. The only information you have is that A conducts electricity, B doesn’t. Question: Which of the two solutions contains potassium bromide (KBr) and which one contains ethanol (CH3CH2OH)? Explain/justify your answer. Answer: Solution

Question: Why a given object is colored orange, i.e. absorbs the blue light, whereas another object is red, i.e. absorbs the green light, while another reflects the whole white light to appear white, another black, another is transparent but colorless? Answer: A/

Answer: 1/ The change is caused by the phenomenon called “Evaporation”. 2/ No, because evaporation takes place at the surface of water (see Figure below), and since the two glasses have different surface (openings), the rates of water evaporation in the two glasses are

You are given two glasses A and B of equal volumes; glass A is tall, has a small base; glass B is short with a larger base. You fill them with water and leave them in the laboratory. After a few days, you examine

You are at sea level and you are boiling water in which a spoon of sugar has been dissolved. Question: Do you expect that solution to boil at: 100oC, <100oC, or >100oC? Justify your answer. Answer: Water in that solution, or any

Answer: Yes, there are some locations where the boiling temperature of water is higher than 100oC, and others where it is lower than 100oC. Remember that the boiling temperature of a liquid is the temperature  at which the vapor pressure of the liquid is

Question: Answer, by Yes or No, if there may be a point/location on the Earth where the boiling point of water is lower or higher than 100oC, and justify your answer.

You have two containers of the same volume. The container A has a fixed or constant volume, the container B has an expandable/expansible volume. You fill the two containers with air at rtp and close them tightly. You want to heat the air

Questions:(1) What’s the definition of pressure and more specifically the atmospheric pressure? (2) Explain how the atmospheric pressure at a given location can affect the performance of an athlete? (3) Do we need to indicate the pressure at which a chemical reaction

Question: One daily phenomenon that we live with is Light. Give a scientific explanation of that phenomenon and the origin of colors. Answer: There are two combined origins or causes of the colors of objects we see: (i) the light, and (ii) the nature

In the Introduction of this Series of Problems and Solutions, Chemistry has been defined as the Science related to the Study and Observation of Matter that we find in our environment and interact with in our daily life; the study of the interaction between

Question: How much energy is lost (produced) or gained when Co-60 undergoes a beta decay? Mass of   Co-60 is 59.9338 g, Mass of Ni-60 is 59.9308 g. Solution: m = 59.9308 g - 59.9338 g = -0.003 g = -0.003 x

A short reminding on ordinary chemical reactions. In a chemical reaction, atoms involved in the reaction do not change, only the way they are combined changes; in other words, only the chemical bonds change during a chemical reaction. The difference between the bond energies

Attention: These exercises apply the principles and theory explained in Issue # 41(Rates of Radioactive decay, Half-life time, Dating). 1/ ln N/No = ln (4min-1/16min-1) = ln 0.25 = -kt t1/2 = 0.693/k = 5,600 years k = 0.693/5,600 y

1/ The radioactive count rate in living organisms due to the presence and decay of C-14 is 16 min-1 per gram of carbon. A wood carving was dug up and found to have a count rate of 4 min-1 per gram of carbon. How

[Source: Understanding Chemistry for Advanced Level, Second Edition, by Ted Lister and Janet Renshaw, p.55-56) Radioisotopes have a larger number of industrial and medical applications. Leak tracing A small amount of a radioisotope, placed in an inaccessible system of pipework such as in

Nuclear Fission: splitting of a heavy atomic nucleus, such as that of Uranium or Plutonium, into two fragments of roughly equal mass. Nuclear Fusion: a reaction through which two or more light nuclei collide to form a heavier nucleus. Nuclear chain reaction: a process

Nuclear radiations bear energy. Depending on their energy, mass and charge, they can penetrate or be stopped by matter, and this is called penetration power. The figures below illustrate this:                                                       (dreamstime.com)                                                                 (cheggy.com) Few explanations on the causes of the penetration power of

Exercises: Complete the following nuclear equations: 1/ 22990Th →   22588Ra +  ? 2/ 10n   →   11p  +  ? 3/ 21684Po   →  0-1e  + ? 4/ 23592U  +  10n (bombardment by neutron)  →  14456Ba  + ?  +  210n 5/ ?   →  23490Th  + α 6/ 23491Pa  →  ? +  β Solutions 1-      22990Th  →  22588Ra + 42α alpha emission (42He) 2-      10n  → 11p  +  0-1e  beta emission (β)

Ref:sas.upenn.edu/⁓mcnemar/apchem/nuclear.pdf Prerequisites: Composition of atom, particularly the composition of atomic nucleus. Nuclear Chemistry Why? Nuclear chemistry is the subdiscipline of chemistry that is concerned with changes in the nucleus of elements. These changes are the source of

Question: Explain the difference between a nuclear reaction and a simple  or ordinary chemical reaction. Answer: The difference between a Nuclear Reaction and a Simple or Ordinary Chemical Reaction: Ordinary Chemistry Nuclear Chemistry 1-Only Valence electrons are involved; the identities of atoms involved do

Questions 1-How long it takes to deposit 0.635 g of Cu at the cathode during the electrolysis of CuSO4(aq) solution, if the current used is of 0.200A?  2-      An industrial cell electrolyzes an aqueous solution of NaCl using a current of

Question: Explain the concept of Electrolytic Cell, draw a representation of it, and give concrete example of application of an Electrolytic Cell. Solution: (i) An Electrolytic Cell is an Electrochemical Cell in which the chemical reaction taking place in the cell is not spontaneous