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3 years ago

How is enthalpy used to predict whether a reaction is endothermic or exothermic?

Chemistry

2 answers:

lana [24]3 years ago

5 0

The correct option is this: WHEN THE ENTHALPY CHANGE OF THE REACTION IS POSITIVE, THE REACTION IS ENDOTHERMIC.
All chemical reactions are divided into two classes, these are exothermic and endothermic reaction. An exothermic reaction is a type of reaction in which energy is lost to the environment, thus the enthalpy change of the reaction is negative. An endothermic reaction is a type of reaction in which energy is absorbed from the environment, thus the enthaply change of the reaction is positive.

UkoKoshka [18]3 years ago

5 0

Answer: When the enthalpy change of the reaction is positive, the reaction is endothermic.

Explanation: Exothermic reactions are defined as the reactions in which energy of the product is less than the energy of the reactants. The total energy is released in the form of heat and $\Delta H$ for the reaction comes out to be negative.

Endothermic reactions are defined as the reactions in which energy of the product is greater than the energy of the reactants. The total energy is absorbed in the form of heat and $\Delta H$ for the reaction comes out to be positive.

$\Delta H=H_{products}-H_{reactants}$

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A forensic chemist is given a white powder for analysis. She dissolves 0.50 g of the substance in 8.0 g of benzene. The solution

Sholpan [36]

Answer:

The given compound cannot be cocaine.

Explanation:

The chemist can comment on the nature of compound being cocaine or not from the depression in freezing point.

Depression in freezing point of is related to molality as:

Depression in freezing point = Kf X molality

Where

Kf = cryoscopic constant = 4.90°C/m

depression in freezing point = normal freezing point - freezing point of solution

depression in freezing point = 5.5-3.9 = 1.6°C

1.6°C = 4.90 X molality

$molality=\frac{1.6}{4.90} = 0.327 m$

we know that:

$molality=\frac{moles}{mass of solvent(kg)}=\frac{moles}{0.008kg}$

therefore

moles = 0.327X0.008 = 0.00261 mol

$moles=\frac{mass}{molarmass}$

$molarmass=\frac{mass}{moles}=\frac{0.50}{0.00261}= 191.57g/mol$

The molar mass of cocaine is 303.353

So the given compound cannot be cocaine.

3 0

3 years ago

Which elements are more likely to lose electrons? Ca, Li, F and Ne

Slav-nsk [51]

Ca, they only have two valence electrons, in order to become more stable, they would like to lose all of them

3 0

3 years ago

A scientist is working in a lab and accidentally combines two liquids that quickly form a solution. Which process could be used

PIT_PIT [208]

Answer:

Distillation

Explanation:

The method of distillation can be used to separate the two liquids, if their boiling point is known. The liquid with lower boiling point will be evaporated and its vapours will be captured, while the liquid with higher boiling point will remail in the container in the liquid state.

7 0

2 years ago

Someone pls help me With this I will make you as brain

RoseWind [281]

The answer to that question is c

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2 years ago

Which is generally stronger, intermolecular interactions or intramolecular interactions? Which is generally stronger, intermolec

Inessa [10]

Answer:

A. Intramolecular interactions are generally stronger.

B. a. Only intermolecular interactions are broken when a liquid is converted to a gas.

Explanation:

A. Which is generally stronger, intermolecular interactions or intramolecular interactions?

Intramolecular interactions, in which electrons are gained, lost or shared, constitute true bonds and are one or two orders of magnitude stronger than intermolecular interactions.

B. Which of these kinds of interactions are broken when a liquid is converted to a gas?

When a liquid vaporizes, the intermolecular attractions are broken, that is, molecules get more separated. However, true bonds are not broken which is why the molecules keep their chemical identity.

7 0

3 years ago