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3 years ago

Consider this reaction: KOH + HBr --> KBr + H2O

Chemistry

2 answers:

True [87]3 years ago

7 0

Answer:

B) It turns clear phenolphthalein pink.

Explanation:

KOH is a basic solution.

It turns red litmus paper turns blue.

It turns clear phenolphthalein pink.

The reagent which reacts with metals to form hydrogen gas is acid.

So, the right choice is:

B) It turns clear phenolphthalein pink.

Ymorist [56]3 years ago

5 0

Answer : the answer is B

Explanation: it turns clear phenolphthein pink

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Why is the combined cycle power generation system so much more efficient that the straight steam cycle?

rewona [7]

Answer:

Because it uses the residual energy of the fluid used by the first engine.

Explanation:

A combined cycle power generation counts with two heat engines that work in tandem from the same source of heat. The engines turn the energy into mechanical energy.

The cycle is much more efficient than the other, almost 60% more.

I hope this answer helps you.

8 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 event is an example of melting?

avanturin [10]

Answer:

A. Wax drips down the side of a lot candle.

Explanation:

The chemical change from solid to liquid. This is a combustion reaction, so carbon dioxide gas and water vapour is also produced but you can't see them

8 0

3 years ago

What is true of a saturated solution?

ollegr [7]

Answer:

A saturated solution is a solution that contains the maximum amount of solute that is capable of being dissolved. At 20°C, the maximum amount of NaCl that will dissolve in 100. g of water is 36.0 g. If any more NaCl is added past that point, it will not dissolve because the solution is saturated.

7 0

3 years ago

What does a exothermic mean in scince

kolezko [41]

An exothermic reaction is one that, through either light or heat, releases energy.

It can be expressed simply as:

reactants --> products + energy

The potential energy at the end of the reaction is always lower than at the beginning of the reaction.

An endothermic reaction is a reaction that absorbs energy from its surroundings.

It is essentially reactants + energy ----> products.

Hope this helps,

Brian

3 0

3 years ago

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