Wilhelm Conrad Roentgen was a German scientist who discovered x-rays through the use of Crookes tube, a tube he used in studying cathode rays that emitted new kinds of invisible ray that was capable of penetrating through a black paper.
After hearing such discovery, Henri Becquerel, a French scientist had also took interest in the connection between the phosphoresence he had already been investigating and the newly discovered rays. He thought that the phosphoresence uranium salts he had been observing and studying might absorb sunlight and emit it as x-rays.
To test such idea which was disproved later on, Becquerel wrapped photographic plates in black paper so that sunlight could not reach them. He then placed the crystals of uranium on top of the wrapped plates and put the whole set up outside, exposed under the sun.
When he developed the plates, he saw an outline of the uranium crystals. He also placed other objects such as coins or cut out metals between the crystals and the photographic film/plate. It also turned out that he could also produced outlines of those shapes.
Answer:
1.930 * 10⁻⁹ mg of Mn⁺² are left unprecipitated.
Explanation:
The reaction that takes place is:
Mn⁺² + S⁻² ⇄ MnS(s)
ksp = [Mn⁺²] [S⁻²]
If the pksp of MnS is 13.500, then the ksp is:
From the problem we know that [S⁻²] = 0.0900 M
We use the ksp to calculate [Mn⁺²]:
3.1623*10⁻¹⁴= [Mn⁺²] * 0.0900 M
[Mn⁺²] = 3.514 * 10⁻¹³ M.
Now we can calculate the mass of Mn⁺², using the volume, concentration and atomic weight. Thus the mass of Mn⁺² left unprecipitated is:
3.514 * 10⁻¹³ M * 0.1 L * 54.94 g/mol = 1.930 * 10⁻¹² g = 1.930 * 10⁻⁹ mg.
Answer:
In this experiment, the period of the pendulum is the dependent variable. There are three independent variables: the pendulum mass, the amplitude of the swing, and the length of the pendulum string.
Explanation:
The answers are A. Pseudoscience is often based only on opinions; D. Pseudoscience often involves explanations of beliefs; E. Pseudoscience includes subjective ideas.
Explanation:
Pseudosciences comprises disciplines or theories that do not follow scientific standards but claim to be factual. This includes areas such as clairvoyance or astrology because this is not based on evidence but subjectivity. Indeed, the base of most pseudosciences are personal beliefs, opinions, or subjective ideas. Moreover, complex theories or methods are created to try to explain these beliefs, but because they do not follow scientific standards they are not considered as valid. In this context, options A, D, and E are correct.
Answer:
A mole is the amount of pure substance containing the same number of chemical units as there are atoms in exactly
12 grams of carbon-12 (i.e., 6.023 X 1023).
Explanation:
