The average atomic mass of the hypothetical element is the sum of the products of the isotopes and their percentage abundance. For this given,
atm = (84.95 amu)(0.371) + (86.95 amu)(0.629)
= 86.208 amu
Thus, the average atomic mass of the element is 86.208 amu.
Explanation:
The answer is 0.5 moles of gold
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.
Color implies visible light, so to answer your question: red light has the longest wavelength (~620 - 740 nm). However, there also exists light with even longer wavelengths that is not visible to the human eye, from infrared light to radio waves (with wavelengths that are meters long!)
Answer: 2mg
Part per million is unit that equal to mg/kg of water or simply
. In this case, you asked how much NaCl needed and know the volume of water(100mL), concentration(20ppm or 20 mg/kg) and water density.
Then, the equation would be
concentration = NaCl weight/ water weight
20 x
mg= NaCl weight/ (100ml x 1g/ml)
NaCl weight= 20x
mg/kg x 100g
NaCl weight= 2000 x
g
NaCl weight= 2x
g = 2mg
