When calcium (ca) bonds with oxygen, it gives up two electrons. what is the charge of the ca ion in this compound?

Answer:

3

Explanation:

The number of moles in 17.5 grams of sodium can be calculated using the formula moles = mass / molar mass. With a molar mass of sodium of about 22.99g/mol, the result of our calculation will be approximately 0.761 moles.

The subject of this question is Chemistry, and it involves the concept of moles. To find the number of moles in a given amount of substance, one would use the formula: moles = mass / molar mass. The molar mass of sodium is approximately 22.99 g/mol.

To calculate the number of moles in 17.5 grams of sodium, you would carry out the following calculation: 17.5 g (the given mass of sodium) divided by 22.99 g/mol (the molar mass of sodium).

Here's the calculation: moles = 17.5 g / 22.99 g/mol = 0.761 moles. So, there are approximately 0.761 moles in 17.5 grams of sodium. This makes the answer to the question '0.761'.

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Answer:

The K energy level or innermost shell of the electron.

Explanation:

The K shell is the innermost shell of an electron and to remove an electron in this shell, it requires the most energy compared to the other shells. An electron can be subdivided into K, L, M, N and so on shells depending on the number of electrons the element possesses. The amount of energy needed to remove electrons from each energy level increasing inwards and this is as a result of the shielding effects of the nucleus of the element. The nucleus shields electrons from been removed from the shells and the distance away from the nucleus by the electrons reduces their staying power. So electrons closer to the nucleus are not easily removed and requires the most energy in case it will be removed.

The percent error of the average result is approximately 8.2%.

To calculate the percent error, use the formula:

[tex]\[ \text{Percent Error} = \left| \frac{\text{Measured Value} - \text{Actual Value}}{\text{Actual Value}} \right| \times 100\% \][/tex]

Given:

Measured Value = Average result =x mL

Actual Value = 34.1 mL

Plug in the values into the formula:

[tex]\[ \text{Percent Error} = \left| \frac{x - 34.1}{34.1} \right| \times 100\% \][/tex]

Now, substitute the average result value (measured value) into the formula. Let's say the average result is 36.9 mL:

[tex]\[ \text{Percent Error} = \left| \frac{36.9 - 34.1}{34.1} \right| \times 100\% \]\[ \text{Percent Error} = \left| \frac{2.8}{34.1} \right| \times 100\% \]\[ \text{Percent Error} = \frac{2.8}{34.1} \times 100\% \]\[ \text{Percent Error} = 0.0821 \times 100\% \]\[ \text{Percent Error} = 8.21\% \][/tex]

So, the percent error of the average result is approximately 8.2%.

Taking into account the definition of density and Avogadro's number,  1.44×10²⁴ molecules of ethanol are present in 140 ml of ethanol.

Density is defined as the property that matter, whether solid, liquid or gas, has to compress into a given space.

In other words, density is a quantity that allows us to measure the amount of mass in a certain volume of a substance. Then, the expression for the calculation of density is the quotient between the mass of a body and the volume it occupies:

[tex]density=\frac{mass}{volume}[/tex]

Avogadro's Number

Avogadro's Number or Avogadro's Constant is called the number of particles that make up a substance (usually atoms or molecules) and that can be found in the amount of one mole of said substance. Its value is 6.023×10²³ particles per mole. Avogadro's number applies to any substance.

In this case, you know that:

Replacing in the definition of density:

[tex]0.789\frac{g}{cm^{3} } =\frac{mass}{140cm^{3} }[/tex]

Solving:

mass= 0.789 [tex]\frac{g}{cm^{3} }[/tex]×140 cm³

mass= 110.46 g

The molar mass of ethanol, that is, the amount of mass present in one mole of the compound, is 46 [tex]\frac{g}{mol}[/tex]. Then the number of moles that 110.46 g of ethanol contain is calculated by:

110.46 g×[tex]\frac{1 mol}{46 g}[/tex]= 2.40 moles

Finally, you can apply the following rule of three: If by definition of Avogadro's number 1 mole of ethanol contains 6.023×10²³ molecules, 2.40 moles contains how many molecules?

amount of molecules= (2.40 moles× 6.023×10²³ molecules)÷ 1 mole

amount of molecules= 1.44×10²⁴ moles

In summary, 1.44×10²⁴ molecules of ethanol are present in 140 ml of ethanol.

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density:

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Avogadro's Number:

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To find out how many molecules of ethanol are in 140 mL of ethanol with a density of 0.789 g/cm³, convert the volume to mass using the density, the mass to moles using the molar mass and moles to molecules using Avogadro's number, yielding approximately 1.44 × 10²´ molecules.

To calculate how many molecules of ethanol are present in 140 mL of ethanol, with a density of 0.789 g/cm³, we'll follow these steps:

We can start by finding the mass:

Then, we convert mass to moles:

And then convert moles to molecules:

So, there are approximately 1.44 × 10²´ molecules of ethanol in 140 mL of ethanol.

A) Endothermic reactions where there is a decrease in entropy.

To determine which type of reaction does not happen spontaneously, we need to consider the Gibbs free energy equation:

Gibbs free energy (G) = Enthalpy (H) - Temperature (T) × Entropy (S)

A reaction is spontaneous if the change in Gibbs free energy (ΔG) is negative.

ΔG = ΔH - TΔS

Where:

ΔH is the change in enthalpy (positive for endothermic reactions, negative for exothermic reactions).

ΔS is the change in entropy (positive for increasing entropy, negative for decreasing entropy).

T is the temperature in Kelvin.

Analysis:

Endothermic reactions with a decrease in entropy:

ΔH > 0 (positive)

ΔS < 0 (negative)

ΔG = ΔH - TΔS

Since ΔH is positive and ΔS is negative, ΔG will be positive if TΔS is not large enough to make ΔG negative. Therefore, this reaction may not be spontaneous.

Exothermic reactions with a decrease in entropy:

ΔH < 0 (negative)

ΔS < 0 (negative)

ΔG = ΔH - TΔS

Although ΔH is negative, TΔS is positive. If ΔH is not sufficiently negative, ΔG can still be positive, making the reaction non-spontaneous.

Endothermic reactions with an increase in entropy:

ΔH > 0 (positive)

ΔS > 0 (positive)

ΔG = ΔH - TΔS

Here, if TΔS is greater than ΔH, ΔG will be negative, making the reaction spontaneous.

Exothermic reactions with an increase in entropy:

ΔH < 0 (negative)

ΔS > 0 (positive)

ΔG = ΔH - TΔS

Both terms are favorable; thus, ΔG will typically be negative, making the reaction spontaneous.

Sodium chloride is soluble in water but silica does not. Hence, addition of water to the sample will separate sodium chloride out.

There are various methods to separate the individual chemical compounds from a mixture of them based on their physical or chemical properties. Distillation, filtration, chromatography, magnetic separation etc are some of the separation methods.

Based on the solubility of compounds, the salts can be separated using a separating funnel by adding a suitable solvent.

For example an acid and its salt can be separated by adding an inorganic acid solvent where the salt is soluble and forms aqueous layer and the acid forms a separate organic layer.

Sodium chloride is highly soluble in water, whereas, silica does not dissolve in water. Because of the presence of oxide layer on silica it is insoluble in water.

Thus, by adding water to the sample the silica will deposits under and the salt solution can be removed out.

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Answer:

Option C, atomic number

Explanation:

In the modern periodic table, elements are arranged in the increasing order of atomic number.

As per the modern periodic law,

When the elements are arranged in the order increasing atomic number, then periodicity in the properties are observed, Periodicity in the properties means similar properties repeated after certain intervals.

In modern periodic table, elements are arranged in 7 periods and 18 groups.

Answer: It spreads forming waves

Explanation:

Radiant energy is the one possessed by electromagnetic waves such as visible light,  (IR) rays, ultraviolet (UV) rays, radio waves, etc. The main characteristic of this energy is that it can be propagated in a vacuum, without the need for any material support.

Other properties are:

- It is in motion continuosly

- Travel through space at the speed of 300,000 kilometers per second

- It spreads forming waves.

Answer:

some mass of the nucleus was lost in the first nuclear reaction.

Explanation:

In a nuclear reaction, mass is converted to energy according to Einstein's equation;

E=∆mc^2 where ∆m is known as mass defect. The mass defect arises due to the conversion of part of the mass of the nucleus into energy in a nuclear reaction. c is the speed of light 3×10^8 ms^-1

By so doing, Albert Einstein confirmed that mass and energy are inter convertible in a nuclear reaction.

The color of the flame for the compound sodium hydroxide (NaOH) is yellowish orange.

Sodium hydroxide or caustic soda can be described as an inorganic compound with the chemical formula NaOH. Sodium hydroxide is a white solid ionic compound containing sodium cations Na⁺ and hydroxide anions OH⁻ ions.

Sodium hydroxide (NaOH) can be defined as a highly caustic base that decomposes proteins at normal ambient temperatures and can cause severe chemical burns.

Sodium hydroxide is a colorless crystalline solid with a boiling point of 1,388 °C. NaOH has a lower solubility in polar solvents such as ethanol and methanol but is highly soluble in water.

Dissolution of sodium hydroxide in water is a highly exothermic reaction where a huge amount of heat is liberated, posing a danger through the possibility of splashing.

The color of the flame for the compound sodium hydroxide, NaOH is yellow-orange due to sodium metal.

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Final answer:

An element that has 54 electrons and a +2 charge is iron, resulting in an Fe2+ ion, also known as the iron(II) ion. For the given exercise, an ion with 34 protons and 36 electrons is a Se2- ion, known as the selenide ion.

Explanation:

The element that forms an ion with 54 electrons and a charge of +2 can be identified by first finding the number of protons in its neutral state, which remains unchanged when it becomes an ion.

Since the element has a +2 charge, it must have two more protons than electrons, giving it a total of 56 protons, which is the atomic number of iron (Fe). Therefore, the element is iron, and the ion is Fe2+, also known as the iron(II) ion or ferrous ion.

Now, to answer the check your learning question: An ion with 34 protons and 36 electrons has two more electrons than protons, indicating a -2 charge. The element with 34 protons is selenium (Se), and the ion is Se2-, known as the selenide ion.

The atom with the greatest number of valence electrons is I: 1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d¹⁰ 4p⁶ 5s² 4d¹⁰ 5p⁵. It has 7 valence electrons in the outermost energy level (5p). Thus, the correct option is option C.

Valence electrons are the electrons in the outermost energy level of an atom and are involved in chemical bonding and reactions. Electronic configuration refers to the arrangement of electrons in an atom, ion, or molecule. It describes the distribution of electrons among different energy levels, orbitals, and subshells within an atom or ion.

The electronic configuration is represented using a notation that indicates the energy levels (principle quantum numbers), subshells (s, p, d, f), and the number of electrons in each subshell. The Aufbau principle, Pauli exclusion principle, and Hund's rule are used to determine the order of filling the orbitals and the spin states of the electrons.

Thus, the ideal selection is option C.

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Material  deposited directly  by s glacier is called  till (answer C)

Explanation

Till is a heterogenous  mixture  of different  sized   material  deposited  by  moving ice.  This type of till is known as lodgement  till.

The other type of till   is deposited  by  the melting  in place of stagnant  ice  and   is referred to as ablation till.

After  deposition, some till are  reworked by  water.

The activity that most resembles atoms in a liquid state would be the soccer players running randomly in all directions, as this mirrors the constrained yet random motion atoms in a liquid state experience.

The student was likely comparing soccer players to atoms in a liquid state in order to describe the random, yet constrained movement atoms in a liquid experience. This is best mirrored by the soccer players if they are 'Running randomly in all directions' (Option C). In a liquid state, atoms are not rigidly fixed in place but nor do they have the freedom to move indefinitely in any direction, unlike in a gaseous state.

The other options, such as players lining up or huddling around the ball, would suggest more organized or confined states- more reminiscent of the solid state. Jumping up and down, depending on the speed and proximity to each other, could either be reminiscent of atoms in a solid state (slow movement, confined within certain boundaries) or a heated liquid/gas state (faster movement, possibility to overcome interatomic forces).

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