Answer:
The correct answer is:
<em>(1) It is important that the sample is dissolved in just enough hot solvent. </em>
Explanation:
The process of recrystallization is important to eliminate the impurities and to obtain better crystals of the solid. The solvent used to perform the recrystallization must have a high dissolution power of the substance to be recrystallized and a low dissolution power of the impurities. This is in order to eliminate most impurities. Furthermore, <em>It is important that the sample is dissolved in just enough hot solvent </em>because this should be easy to remove after the recrystallization and the crystal should form easily when the solution cools. Also, it is better to add the hot solvent to solubilize the crystals and keep the impurities insoluble, instead of adding the cold solvent and heating the solution. Additionally, the process of cooling the solution must be done slowly to obtain large and fewer crystals. A fast ice-cooling will form smaller crystals.
By looking at a periodic table, we can conclude that the molar mass of lithium is 6.94g, the molar mass of zinc is 65.38g, and the molar mass of gold is 196.97g. Each of these quantities contains 6.02×1023 atoms of that particular element. The units for molar mass are grams per mole, or g/mol.
So The answers are Lithium, Gold, Zinc
Hope This Helps
~Zero~
Answer:
(a) Ethyl acetate and hexane, and (c) methanol and methylene chloride.
Explanation:
re-crystallization is a technique used to purify solid compound. Ethyl acetate and hexane are good solvent pair for recrystallization because they are miscible with each other due to their good differences in polarity. ethyl acetate has polarity of 77 while hexane has 68.
water and diethyl ether are not good solvent pair for recrystallization because water and diethyl ether are immiscible. They have very far polarity values. water has 100 while diethyl ether has 35
The green and black symbols refer to atoms, that make up the molecule of water, more specifically you can say that the 2 Hydrogen atoms are the black ones found outside, while the central atom, that is also green would be oxygen.
Answer:
The correct answer is 532 K
Explanation:
The Gay-Lussac law describes the behavior of a gas at constant volume, by changing the pressure or temperature. When is heated, the change in pressure of the gas is directly proportional to it absolute temperature (in Kelvin or K).
We have the following initial conditions:
P1= 71.8 kPa
T1= -104ºC +273 = 169 K
If the pressure increases until reaching 225.9 kPa (P2), we can calculate the final temperature of the gas (T2) by using the Gay-Lussac derived expression:
P1 x T2 = P2 x T1
⇒T2= (P2 x T1)/P1 = (225.9 kPa x 169 K)/71.8 kPa= 531.7 K ≅ 532 K
