Fe 3+ + SCN- --> FeSCN 2+
<span>.......Fe 3+.......SCN-.........FeSCN 2+ </span>
<span>I.......0.04..........0.001.............. </span>
<span>C........-x...............-x............. </span>
<span>E.....0.04-x.....0.001-x...........x </span>
<span>Keq = 203.4 = x / (0.04-x)(0.001-x) </span>
<span>203.4 = x / (x^2 - 0.041x + 4x10^-5) </span>
<span>203.4x^2 - 8.34x + 0.00094 = x </span>
<span>203.4x^2 - 9.34x + 0.00094 = 0 </span>
<span>x = -0.0001M or 0.0458M </span>
<span>therefore, according to the calculated Keq, all of the SCN- and Fe 3+ would be fully converted into FeSCN 2+</span>
3 first significant figure
6 second significant figure
5 third significant figure
4 cannot exceed 5, so retain 5 instead of increasing it to 6
0.0365
The mass is 150,000 grams. Multiply 100 by 50 by 30 to determine the container's volume, which equals 150,000 cm^3. Since a milliliter is equivalent to one cubic centimeter, and given that the density of water is one gram per milliliter, it follows that the mass of water is 150,000 grams.
From the provided data, the unknown mixture was composed of salt, salicylic acid, and sand. It is understandable that the student suspected the presence of sand, yet scientific experimentation must verify such assumptions. The test involving salt and salicylic acid reveals that salt dissolves in water, while salicylic acid is only slightly soluble, and sand does not dissolve at all. By introducing the unknown into water, the salt would dissolve first, followed by the partial dissolution of salicylic acid. Heating the mixture could allow for the evaporation of salicylic acid, resulting in the remaining salt. If traces of sand were observed in the dissolved sample, it could suggest contamination.
Your Question: There are two kinds of elements that didn't appear on the periodic table until after 1892. What kinds are they and why do you think it took so long to discover them?
The Answer: The insights of Moseley led chemists to further refine the periodic table and uncover additional gaps, indicating that several new elements, specifically with atomic numbers 43, 61, 72, and 75, remained undiscovered. These elements were later identified as technetium, promethium, hafnium, and rhenium, respectively.
Explanation: Physicist Henry Moseley used x-rays to determine the atomic number of elements, which facilitated a more accurate organization of the periodic table. His life and the discovery of the correlation between atomic number and x-ray frequency, known as Moseley's Law, are significant to note.
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