Which sentence describes the energy changes that occur when a chemical reaction happens?

Answer:

b

Explanation:

because it is the balanced one

The change in the free energy of the reaction  is given by  207.3 kJ.

The change in free energy (ΔG) is a measure of the maximum amount of work that can be extracted from a chemical reaction. It is calculated as the difference between the free energy of the products and the free energy of the reactants, and is expressed in units of energy (such as joules or calories) per mole of reaction.

Using the formula;

ΔG = ΔH - TΔS

ΔG = 163.2 - (298 * (-148))

ΔG = 207.3 kJ

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Answer:

A ---->gamma ray

Explanation:

Gamma rays have the highest frequencies among all electromagnetic waves and therefore have the shortest wavelengths.

Considering the definition of pH, the pH of a 3.4×10⁻⁶ M solution of HNO₃ is 5.47.

pH is a measure of acidity or alkalinity and indicates the amount of hydrogen ions present in a solution or substance.

The pH is defined as the negative base 10 logarithm of the activity of hydrogen ions:

pH= - log [H⁺]

Strong acids are those that are completely, or almost completely, dissociated in dilute solution (of concentration less than 0.1 M). So the concentration of protons is equal to the initial concentration of acid.

HNO₃ is a strong acid. So [H⁺]= [HNO₃]= 3.4×10⁻⁶ M

So, the pH can be calculated as:

pH= - log (3.4×10⁻⁶ M)

Solving:

pH= 5.47

Finally, the pH is 5.47.

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Answer:

One can draw the 3-dimensional structure of an atom once they have the Lewis Structure of an atom. The 3-dimensional geometrical structure of ammonium, NH4+ is referred to as Tetrahedral. ... But the + sign decrees that NH4+ has 8 valence shell electrons, due to the positive ion.

Explanation:

The mole of the substance, given the data from the question is 0.0014 mole

This is simply defined as the mole of solute per kilogram of water. Mathematically, it is expressed as

Molality = mole / mass (Kg) of water

Mole = molality × mass of water

Mole of substance = 0.056 × 0.0254

Mole of substance = 0.0014 mole

Thus, the mole of the substance is 0.0014 mole

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Answer:

When the light energy from sunlight hits matter, heat energy is formed

Answer:

A

Explanation:

when light energy hit matter heat energy formed

Answer: Oxygen

Explanation: Its found on the periodic table as an element.

Answer:

The Correct answer is 15

Answer:

B). 15

Explanation:

Answer:

Crop rotation

Explanation:

The growing of different crops in succession on a piece of land to avoid exhausting the soil and to control weeds,pets,and diseases

Answer:

Sr(NO3)2 + Na2CO3 --------> SrCO3 + 2NaNO3

Total ionic equation;

Sr^2+ + NO3^- + Na^+ + CO3^2- -----> SrCO3 + 2NaNO3

Net ionic equation;

Sr^2+ + CO3^2- -----> SrCO3

Explanation:

The molecular equation shows the reactions of the compounds to give the products. It shows the molecular formula of reactants and products.

The total ionic equation shows the ions that recombine to form the products of the reaction.

The net ionic shows the major ionic reaction that took place in the system.

Hence, the net ionic equation explicitly shows the major species that are involved in a reaction, while a complete ionic equation includes the spectator ions.

Balanced chemical equation:

\(Sr(NO_3)_2 + Na_2CO_3 --> SrCO_3 + 2NaNO_3\)

Total ionic equation:

\(Sr^{2+} + NO_3^{-} + Na^+ + CO_3^{2-} --> SrCO_3 + 2NaNO_3\)

Net ionic equation:

\(Sr^{2+} + CO_3^{2-} --> SrCO_3\)

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Answer:

Density is commonly used in units of grams per cubic centimetre.

Answer:

g/cm^3

Explanation:

Density=mass/volume = g/cm^3 and it is commonly expressed unit. But if you want, you can also convert it into kg/m^3 .

Answer:

B. Eastern Europe

Explanation:

The economy of Eastern Europe depends on producing foods. For example, Poland and Belarus are two countries in Eastern Europe, and they both produce chocolates. Producing foods isn't the only detrimental part of the region's economic data. The other half depends on consumer goods. For example, Estonia and Latvia are good countries in packaging food. The answer to the question is B.

The final temperature of the water is: T_final = 45.0°C

We can use the formula for the specific heat capacity of the water to solve this problem:

q = mcΔT

First, we can calculate the initial energy of the water:

q = mcΔT

q = (10.0 g) (4.184 J/g°C) (25.0°C)

q = 1,046 J

Next, we can calculate the final temperature after absorbing 840 J:

q = mcΔT

840 J = (10.0 g) (4.184 J/g°C) (ΔT)

ΔT = 20.0°C

Therefore, the final temperature of the water is:

T_final = T_initial + ΔT

T_final = 25.0°C + 20.0°C

T_final = 45.0°C

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The number of moles of cobalt (Co) atoms in 9.0 x 10⁹ Co atoms is 1.49 × 10-¹⁴ moles.

The number of moles of a substance can be calculated by dividing the number of atoms of the substance by Avogadro's number as follows:

no of moles = no of atoms ÷ Avogadro's number (6.02 × 10²³)

According to this question, 9.0 x 10⁹ cobalt atoms is given. The number of moles can be calculated as follows:

no of moles = 9.0 x 10⁹ ÷ 6.02 × 10²³

no of moles = 1.49 × 10-¹⁴ moles

Therefore, 1.49 × 10-¹⁴ moles of cobalt are in 9 billion atoms of the element.

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Na (sodium) and F (fluorine) can bond because they have different electronegativities. Electronegativity is a measure of an atom's ability to attract electrons to itself. Fluorine is one of the most electronegative elements on the periodic table, while sodium is one of the least electronegative. This creates an electrostatic attraction between the two atoms, allowing them to form a chemical bond. The bond between Na and F is called an ionic bond.

The ionic bond between Na and F is formed when the sodium atom loses one electron to form a Na+ cation, and the fluorine atom gains one electron to form a F- anion. The resulting molecule is NaF.

Be (beryllium) and Br (bromine) can bond because they also have different electronegativities. Be is less electronegative than Br, and this creates an electrostatic attraction between the two atoms, allowing them to form a chemical bond. The bond between Be and Br is called a covalent bond.

The covalent bond between Be and Br is formed when both atoms share electrons. The resulting molecule is BeBr2 (Beryllium dibromide).

In general, it's important to note that the type of bond formed between two atoms depends on their electronegativities, if they are similar they tend to form covalent bond and if they are different they tend to form ionic bonds.

Answer:

a is oxidation

b is reduction

c is reduction

d is oxidation

hope it helps you

Oxygen-16: 8 protons, 8 neutrons, 8 electrons

Oxygen-18: 8 protons, 10 neutrons, 8 electrons

Using atomic and mass numbers, we can find information about the makeup of atoms.

Protons

Every element has a unique number of protons, and every atom of the same element will have the same number of protons. This means that both oxygen atoms must have the same number of protons. The number of protons in an element is equal to its atomic number. Since oxygen has an atomic number of 8, all oxygen atoms will have 8 protons. This means that oxygen-16 and oxygen-18 have 8 protons.

Neutrons

The number of neutrons an atom of a certain element can have varies. Atoms of the same element that have different numbers of neutrons are known as isotopes. The number of neutrons can be found through the mass number. The mass number is the number that follows the dash in the name of the isotope. This number is equal to the protons plus the neutrons. So, to find the number of neutrons in an oxygen atom, subtract 8 protons from the mass number. This means oxygen-16 has 8 neutrons and oxygen-18 has 10 neutrons.

Electrons

Remember that electrons are negatively charged, protons are positively charged, and neutrons have no charge. The number of electrons in an atom determines the charge of the atom. If the number of electrons equals the number of protons, then the charge of the atom will equal 0. If there are more electrons, then the atom will be negatively charged and vice versa. Since neither of the atoms has any indication of a nonzero charge, the number of electrons must equal the number of protons. So, both oxygen atoms have 8 electrons.

This representation suggests that the element is phosphorus (P) with a mass number of 30, which is incorrect. The correct mass number for phosphorus is approximately 30.97. The incorrect representation for a neutral atom is 36Li

To determine the correct representation for a neutral atom, we need to consider the atomic number (Z) and mass number (A) of the element. The atomic number represents the number of protons in the nucleus, while the mass number represents the sum of protons and neutrons.

Let's analyze the given representations:

36Li:

This representation suggests that the element is lithium (Li) with a mass number of 36, which is incorrect. The correct mass number for lithium is approximately 6.94.

613C:

This representation suggests that the element is carbon (C) with a mass number of 13, which is correct. Carbon has different isotopes, and 13C represents one of its stable isotopes.

3063Cu:

This representation suggests that the element is copper (Cu) with a mass number of 63, which is correct. Copper has different isotopes, and 63Cu represents one of its stable isotopes.

1530P:

This representation suggests that the element is phosphorus (P) with a mass number of 30, which is incorrect. The correct mass number for phosphorus is approximately 30.97.

Therefore, the incorrect representation for a neutral atom is 36Li, as it does not match the known properties of lithium.

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Answer:

neon sulfur iodine xenon

1) Isotopes. Two atoms that have the same number of protons but a different number of neutrons.

2) Isotopes of Silicon.

Mass number: 28

Atomic number: 14

Electrons: 14

Neutrons = mass number - atomic number = 14

Mass number: 29

Atomic number: 14

Electrons: 14

Neutrons = mass number - atomic number = 15

3) Similarities and differences

These two isotopes of Silicon have the same number of protons and electrons.

14 protons and 14 electrons

These two isotopes of Silicon have different mass numbers and neutrons.

The first one, mass number 28 and 14 neutrons.

The second one, mass number 29 and 15 neutrons.

.

Answer: C

Explanation: I got it right.

Answer:

a

Explanation:

electrons can be superchared if fast enouf

The transition of electrons within the atoms or ions produces spectral lines. The line spectra is also known as the atomic spectra. The correct option is A.

The line spectra can be defined as the spectrum consisting of electromagnetic radiation which is emitted or absorbed by an electron due to transition between the energy levels within an atom.

During the excitation of an electron from one energy level to another there occurs the emission or absorption of light of particular wavelengths. The collection of all these particular wavelengths in a fixed conditions of pressure, temperature etc. is called the line spectra.

A thin band consisting of bright or dark light is defined as the spectral line. They are generally used to identify the atoms and molecules. There exists unique sets of spectral lines for every atom and molecule.

The series of coloured lines produced as a result of the transition of electrons between different energy levels are known as line spectra.

Thus the correct option is A - Electrons.

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The considerations which are applicable in a suitable recrystallization solvent are: should have a boiling point that is ~ 30-50 °C, Should be unreactive, Offers minimal solubility and solubility-temperature relationship. Option A, C, D and E will be correct.

This statement is true. Because the solvent should have a boiling point that is around 30-50 °C higher than the melting point of the compound to be recrystallized in order to achieve efficient dissolution and crystal formation.

This statement is false. Because a good recrystallization solvent should dissolve the compound of interest well at high temperatures but not at all or only slightly at lower temperatures. Ideally, the impurities should dissolve well at all temperatures, so that they can be separated from the compound of interest during the filtration step.

This statement is true. Because the solvent should not react with the compound of interest, which would affect the purity of the final product.

This statement is true. Because the solvent should have minimal solubility for the compound to be purified at room temperature and lower temperatures, but should dissolve the compound well at higher temperatures in order to achieve efficient recrystallization.

This statement is true. Because the solubility-temperature relationship for the solvent and the compound should have a low slope in order to achieve efficient recrystallization.

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--The given question is incorrect, the correct question is

"Which of the following considerations are applicable when choosing a suitable recrystallization solvent? (TRUE / FALSE) A) Should have a boiling point that is ~ 30-50 °C above room temperature. B) Does not dissolve impurities at all temperatures or completely dissolves impurities at all temperatures. C) Should be unreactive toward the compound of interest. D) Offers minimal solubility of the compound to be purified at room and lower temperatures. E) Its solubility-temperature relationship to the compound should give a curve with a low slope."--

Answer:

IS IT MULTIPLE CHOICE

Explanation:

Answer:

B. are openings in the earth surface

Answer:

it is a soft and very cold molocules but at the touch of a hand it will melt because of how compact the molocules are

Explanation:

gallium can only stay a solid under 85.59°F so is someone had is in there had is would end up like ice cream

It is essential to learn the usage of fire extinguishers before doing practical work in the laboratory as a fire can arise at any time.

Before performing practical work in lab, learning how to use a fire extinguisher is crucial because fires can happen unexpectedly in a lab. This can be due to variety of reasons, including electrical faults, chemical reactions, or human error. Understanding how to use a fire extinguisher can assist keep small fires from escalating and harming people, property, or the lab itself.

Aside from that, different fires call for various fire extinguishers. For example, it is best to avoid using water-based fire extinguishers on electrical or chemical fires since they may worsen the situation. It is crucial to understand how to choose and utilise the appropriate fire extinguisher for the sort of fire that can develop in the laboratory.

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