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Answer:</h2><h2>The primary requirement for good melting point determination is that the sample be in a fine powder form. This makes the heat transfer into the sample more efficient and reproducible, and also enhances the overall reflectivity of the sample for easier automated detection of the melt</h2><h2 />
It's your hw so you really should understand it so you dont have to ask for help so I'll try to explain it the best I can.
1.SD (only one switch occurs, between fluorine and bromide)
2.DD (two things are switched, sulfate and nitrate)
3. D (One compound is broken up into smaller compounds)
4.C (The products of combustion are always h20 and co2)
5.DD (again, two things are switched, bromide and nitrate)
6.SD (In SDR, look for a lone molecule reacting with a compound)
7.S (two smaller compounds become one big compound)
8. D( A big compound is broken up)
9. DD (I think Its DD because two molecules were displaced)*not sure
10.DD(two molecules are displaced, phosphate and hydroxide)
The base dissociation constant or Kb is a value used to measure
the strength of a specific base in solution. To determine the percent ionization
of the substance we make use of the Kb given. Methylamine or CH3NH2 when
in solution would form ions:
CH3NH2 + H2O < = > CH3NH3+ + OH-
Kb is expressed as follows:
<span>
Kb = [OH-] [CH3NH3+] / [CH3NH2]
Where the terms represents the concentrations of the acid and the ions.
By the ICE table, we can calculate the equilibrium concentrations,
CH3NH2 CH3NH3+
OH-
I 1.60 0
0
C -x +x
+x
--------------------------------------------------
E 1.60-x x
x
Kb = [OH-] [CH3NH3+] / [CH3NH2] = </span> 3.4×10−4
<span> 3.4×10−4</span> = x^2 / 1.60-x
Solving for x,
x = [OH-] = 0.023 M
pH = 14 + log 0.023 = 12.36
Therefore, the first option is the closest one.
Avogadro's number represents the number of units in one mole of any substance. This has the value of 6.022 x 10^23 units / mole. This number can be used to convert the number of atoms or molecules into number of moles. This value was experimentally determined by Amedeo Avogadro.
Molarity is expressed as
the number of moles of solute per volume of the solution. The mass of oxalic acid dihydrate needed for the solution is calculated as follows:
Amount in moles: (0.357 mol H2C2O4•2H2O / L) (.250 L ) = 0.0893 mol H2C2O4•2H2O
Amount in mass : 0.0893 mol H2C2O4•2H2O (126.08 g / mol ) = 11.2589 g H2C2O4•2H2O
Hope this answers the question. Have a nice day.