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4 years ago

What is the difference between melting and melting point

Chemistry

1 answer:

Yakvenalex [24]4 years ago

4 0

Answer:

Melting Is when a substance is actually melting and melting point is a point at which a substance is able to melt.

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Which of the following is not true of alloys?

Scilla [17]

Option d: copper.

Because copper is an element, not a mixture.

7 0

4 years ago

Measure out 2.87 moles of sodium chloride (Nacl) into a clean dry cup.

Anettt [7]

Answer: weigh is m = n × M = 2.87 mol × 58.44 g/mol

Explanation: mass = amount of substance × molar mass

M((NaCl) = 22.99 +35.45

6 0

3 years ago

A 0.020 M solution of niacin has a pH of 3.26. (a) What percentage of the acid is ionized in this solution

mariarad [96]

Answer: 2.75%

Explanation:

$pH=-log [H+]$

$3.26 = -log [H+]$

$[H+] = 5.495\times 10^{-4} M$

$HA\rightleftharpoons H^++A^-$

initial 0.020 0 0

eqm 0.020 -x x x

$K_a=\frac{[H+][A-]}{[HA]}$

$K_a=\frac{[x][x]}{[0.020-x]}$

$x=5.495\times 10^{-4}$

$K_a=\frac{[5.495\times 10^{-4}]^2}{[0.020-5.495\times 10^{-4}]}$

$K_a =1.553\times 10^{-5}$

percent dissociation = $\frac{[H^+_eqm]}{[Acid_{initial}]}\times 100$

percent dissociation= $\frac{5.495\times 10^{-4}}{0.020}\times 100$

Thus percent dissociation= 2.75 %

5 0

3 years ago

"Thermite" reactions have been used for welding metal parts such as railway rails and in metal refining. One such thermite react

frosja888 [35]

<u>Answer:</u> The given reaction is non-spontaneous in nature.

<u>Explanation:</u>

Entropy change is defined as the difference in entropy of all the product and the reactants each multiplied with their respective number of moles.

The equation used to calculate entropy change is of a reaction is:

$\Delta S^o_{rxn}=\sum [n\times \Delta S^o_{(product)}]-\sum [n\times \Delta S^o_{(reactant)}]$

For the given chemical reaction:

$3Mg(s)+Cr_2O_3(s)\rightarrow 3MgO(s)+2Cr(s)$

The equation for the entropy change of the above reaction is:

$\Delta S^o_{rxn}=[(3\times \Delta S^o_{(MgO(s))})+(2\times \Delta S^o_{(Cr(s))})]-[(3\times \Delta S^o_{(Mg(s))})+(1\times \Delta S^o_{(Cr_2O_3(s))})]$

We are given:

$\Delta S^o_{(Mg(s))}=32.68J/K.mol\\\Delta S^o_{(Cr_2O_3(s))}=81.2J/K.mol\\\Delta S^o_{(MgO(s))}=26.94J/K.mol\\\Delta S^o_{(Cr(s))}=23.77J/K.mol$

Putting values in above equation, we get:

$\Delta S^o_{rxn}=[(3\times (26.94))+(2\times (23.77))]-[(3\times (32.68))+(1\times (81.2))]\\\\\Delta S^o_{rxn}=-50.88J/K=-0.0509kJ/K.mol$

For the reaction to be spontaneous, the Gibbs free energy of the reaction must come out to be negative.

To calculate the standard Gibbs free energy of the reaction, we use the equation:

$\Delta G^o=\Delta H^o-T\Delta S^o$

where,

$\Delta G^o$ = standard Gibbs free energy = ?

$\Delta H^o$ = standard enthalpy change of the reaction = 665.1 kJ/mol

T = Temperature = 298.15 K

$\Delta S^o$ = standard entropy change of the reaction = -0.0509 kJ/K.mol

Putting values in above equation, we get:

$\Delta G^o=(665.1kJ/mol)-(298.15K\times (-0.0509kJ/K.mol))=680.27kJ/mol$

As, the Gibbs free energy of the reaction is coming out to be positive, the reaction is non-spontaneous in nature.

Hence, the given reaction is non-spontaneous in nature.

4 0

4 years ago

Which compound will precipitate when solutions of iron(II) acetate, Fe(C2H3O2)2, and potassium iodide (KI) are mixed?

oksano4ka [1.4K]

FeI2 (B). Group 1 elements (K) dissociate completely, so KCH3CO2 will become K+ and CH3CO2- . Fe2+ and I- don't dissociate in water, so you get FeI2(s) precipitate.

8 0

3 years ago

Read 2 more answers