Answer=4
Only solids can create regular geometric patterns... CO2 is a gas, H2O is a liquid and Sodium Chloride doesn't count because it's dissolved in a solution...
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.
The mass of Ca(CN)2 : 92,11 g/mol
<h3>Further explanation</h3>
Given
0.0321 moles of Ca(CN)2
Required
The mass
Solution
The mole is the number of particles contained in a substance
1 mol = 6.02.10²³
Moles can also be determined from the amount of substance mass and its molar mass
mol(n) = mass(m) : MW(molecular weight)
Input the value :
mass = mol x MW Ca (CN)2
mass = 0.0321 x 92,11 g/mol
mass = 2.957 g
Answer:
Period
Explanation:
Elements are listed in order of increasing atomic number from left to right. Each row of the periodic table is called a period and each column of the periodic table is called a group (or family). Some groups have specific names like the halogens or noble gases.
When presented with balanced chemical equation, the same phase can be cancelled out only when they appear to be in the opposite side of the equation. This means that in one equation, a certain chemical is a product. However, on the next equation, that same substance can be the reactant.