Which of the following is a description of an exothermic reaction?

A. releases heat
B. reactants have less enthalpy than the products
C. ∆H is positive
D. gets cold

Answers

Answer 1

A description of an exothermic reaction is it releases heat. The correct option is A.

What is an exothermic reaction?

An exothermic reaction is a reaction in which heat is released into the atmosphere. In these reactions, less energy is needed to start the reaction and the energy is released when bonds are made in the products. Delta H is always negative in these reactions.

Energy is always given off when the reaction happened, in the form of heat and light. Examples are burning of wood, melting of ice, combustion, corrosion, etc.

Thus, the correct option is A. releases heat regarding a description of an exothermic reaction.

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Related Questions

Name some coping skills that can be used besides
nicotine vape and or vaping marijuana.

Answers

Exercise, drinking water, friends, anything that can take your mind off those topics
Spend time with your friends or family, being socially active helps me in a lot of things, spend time doing your hobbies..

what variables effect whether or not the fishing weight floats

Answers

Answer:The fishing way and how fast is going

Explanation:Because of the variables the fishing we will flow much more faster

How many moles of calcium are in 5.82g of calcium?

Answers

Answer:

0.024951344877489 mole.

Explanation:

y

An increase in temperature usually slows down a chemical reaction.

True or false? Because?

Answers

The answer to this question is false

2. Jacy bought a gold necklace weighing 21.3 grams from a flea market She filled a 10ml graduated cylinder with water to the 50 mL mark and dropped her necklace in. The level in the graduated cylinder rose to 7.4mL is her necklace real or fake? If not, identify the possible composition of her necklace
Gold: 19.3 g/cm^3
Copper 8.86 g/cm^3
Bronze: 9.87 g/cm^3​

Answers

Answer:

The necklace is fake.

The necklace is made up of copper.

Explanation:

The following data were obtained from the question:

Mass of the necklace = 21.3 g

Volume of water = 5 mL

Volume of water + Necklace = 7.4 mL

To identify the composition of the necklace, we shall determine the density of the necklace.

This can be obtained as follow:

We'll begin by calculating the volume of the necklace. This can be obtained as shown below:

Volume of water = 5 mL

Volume of water + Necklace = 7.4 mL

Volume of Necklace =.?

Volume of Necklace = (Volume of water + Necklace) – (Volume of water)

Volume of Necklace = 7.4 – 5

Volume of Necklace = 2.4 mL

NOTE:

1 mL = 1 cm³

Therefore,

Volume of Necklace = 2.4 mL = 2.4 cm³

Finally, we shall determine the density of the necklace as follow:

Mass of the Necklace = 21.3 g

Volume of Necklace = 2.4 cm³

Density of Necklace =?

Density = mass /volume

Density = 21.3 / 2.4

Density = 8.87 g/cm³

Therefore, the density of the necklace is 8.87 g/cm³.

From the question given above, we were told Jacy bought a gold necklace.

But comparing the density of necklace to the densities given above the necklace is obviously made of copper material.

Therefore, Jacy bought a fake gold necklace.

If ΔH vaporization of water (H2O) is 40.7 kJ/mol,
and the ΔS for vaporization of H2O is 109 J/mol K,
what is ΔG for water vaporization at 350K?
Include units.

Answers

Answer:

2.6 kJ/mol

Explanation:

Step 1: Given data

Standard enthalpy of vaporization of water (ΔH°): 40.7 kJ/molStandard entropy of vaporization of water (ΔS°): 109 J/mol.KAbsolute temperature (T): 350 KStandard Gibbs free energy of vaporization of water (ΔG°): ?

Step 2: Calculate ΔG°

We can calculate ΔG° using the following expression.

ΔG° = ΔH° - T × ΔS°

ΔG° = 40.7 kJ/mol - 350 K × 0.109 kJ/mol.K

ΔG° = 2.6 kJ/mol

The change in Gibbs free energy, ΔG for the water is 2.55 KJ/mol

Data obtained from the question

From the question given above, the following data were obtained:

Standard enthalpy of vaporization of water (ΔH°) = 40.7 kJ/molStandard entropy of vaporization of water (ΔS°) = 109 J/Kmol = 109 / 1000 = 0.109 KJ/Kmol Absolute temperature (T) = 350 KStandard Gibbs free energy (ΔG°) =?

How to determine the Gibbs free energy, ΔG°

The Gibbs free energy, ΔG° can be obtained as illustrated below:

ΔG° = ΔH° – TΔS°

ΔG° = 40.7 – (350 × 0.109)

ΔG° = 40.7 – 38.15

ΔG° = 2.55 KJ/mol

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Explain why CaCl2 is likely to have properties similar to those of CaBr2

Answers

Answer:

Because both CaCl2 and CaBr2 both contain elements (Chlorine and Bromine) from the same group (group 7)

Explanation:

Elements are placed into different groups in the periodic table. Elements in the same group are those that have the same number of valence electrons in their outermost shell and as a result will behave similar chemically i.e. will react with other elements in the same manner.

Chlorine and Bromine are two elements belonging to group 7 of the periodic table. They are called HALOGENS and they have seven valence electrons in their outermost shell. Hence, when they form a compound with Calcium, a group two element, these compounds (CaCl2 and CaBr2) will possess similar properties because they have elements that are from the same group (halogen group).

The compounds of [tex]\rm CaCl_2[/tex] and [tex]\rm CaBr_2[/tex] have similar chemical properties as they are constituted of elements belonging to the same group.

The compounds with the elements belonging to the same group have similar chemical properties. It has been given that the chemical properties of elements have been dependent on the number of valence electrons.

The given compounds have been calcium chloride and calcium bromide. The calcium has been the same cation in the compounds however, the anions are different.

The anion Cl and Br both belongs to group 17 and have 7 valence electrons. Thus, the compounds have been possessing similar chemical properties.

Thus, calcium chloride and calcium bromide are more likely to have similar chemical properties as they have elements belonging to the same group.

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What is the average pressure exerted by the molecules on the walls of the container?

Answers

Answer:

This question appears to be incomplete

Explanation:

However, we know that one of the kinetic theories of gases is that gas molecules collide with one another and against the walls of the container (in which they are stored); hence exerting there pressure on the walls of this container.

Ideal gases are the most suitable for this theory because it's molecules are far apart and do not exert any attractive forces towards one another; hence it's molecules move "undisturbed" or "freely". For ideal gases, the average pressure exerted by by the gas molecules on the walls of the container can be calculated as

PV = nRT

Where P = pressure (in atmosphere, atm or kilopascal, KPa or millimeter mercury, mmHg)

V = volume (in liters)

n = number of molecules

R = ideal gas constant (8.3145 J·mol⁻¹·K⁻¹)

T = temperature (in kelvin)

any help with these questions would help i'm lost

Answers

Answer:

1.  31.25 mL

2.  1.98 g/L

3.  0.45 g/mL

Explanation:

For each of the problems, you need to perform unit conversions.  You need to use the information given to you to convert to a specific unit.

1.  You need volume (mL).  You have density (g/mL) and mass (g).  Divide mass by density.  You will cancel out mL and be left with g.

(50.0 g)/(1.60 g/mL) = 31.25 mL

2.  You are given grams and liters.  You need to find density with units g/L.  This means that you have to divide grams by liters.

(0.891 g)/(0.450 L) = 1.98 g/L

3.  You have to find density again but this time with units g/mL.  Divide the given mass by the volume.

(10.0 g)/(22.0 mL) = 0.45 g/mL

what is the density or 40 mL of liquid that has a mass of 20 grams help ASAP​

Answers

Answer:

Density of 40 mL of liquid that has a mass of 20 g = 20 / 40 = 0.5 g / cc

Answer:

Density= mass/volume

Density= 20/40

Density= 0.5g/mL

Which of the following represents the least number of molecules?
(a) 20.0 g of H2O (18.02 g/mol)
(b) 77.0 g of CH4 (16.06 g/mol)
(c) 68.0 g of CaH2 (42.09 g/mol)
(d) 100.0 g of N2O (44.02 g/mol)
(e) 84.0 g of HF (20.01 g/mol)

Answers

Answer:

A ; 20g of water has the least number of molecules

Explanation:

Here, we want to know which of the options represent the least number of molecules;

To calculate this, we are going to first calculate the number of moles using the formula below;

Number of moles = mass/molar mass

Then from the number of moles, we can calculate the number of molecules by multiplying the number of moles by 6.02 * 10^23 molecules

Let’s proceed;

a. That will be 20/18.02 = 1.1099 moles

1.1099 * 6.02 * 10^23 = 6.68 * 10^23 molecules

b. That will be 77/16.06 = 4.8 moles

4.8 * 6.02 * 10^23 = 2.89 * 10*24 molecules

c. That will be 68/42.09 = 1.62 moles

1.62 * 6.02 * 10^23 = 9.73 * 10^23 molecules

d. That will be 100/44.02 = 2.27 moles

2.27 * 6.02 * 10^23 = 1.37 * 10^24 molecules

e. That will be = 84/20.01 = 4.2 moles

4.2 * 6.02 * 10^23 = 2.53 * 10^24 molecules

From all the values obtained, the lowest is 20g of water

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