#1: Which element has the same number of valence electrons as hydrogen (H)?

A. helium (He)

B. oxygen (O)

C. nitrogen (N)

D. lithium (Li)


***my answer: D. lithium (Li)

is that right?

The answer is 6mm

You're welcome!

3 would be the answer to your question...

Answer:

There will many opportunities in the field of renewable energy science and engineering. It is an exciting field, with a lot of variety and room for new ideas.

Explanation:

Answer:Sample Response:

There will many opportunities in the field of renewable energy science and engineering. It is an exciting field, with a lot of variety and room for new ideas.

Explanation:

What did you include in your response? Check all that apply.

opportunities

exciting field

variety

room for new ideas

Substances with weaker intermolecular forces evaporate faster due to higher vapor pressure and volatility.

Substances with weaker intermolecular forces evaporate faster than substances with stronger intermolecular forces.

Weak intermolecular forces lead to a higher vapor pressure and increased volatility in substances, causing them to evaporate at a faster rate.

Answer: chromatography

Explanation:

Chromatography : It is a type of separation process in which the liquid or gas is separated into components at different rate. The principle of chromatography is that the substance of molecule are distributed between the liquid phases. It involves a stationary and a mobile phase.  Hence,chromatography is a laboratory technique that is used to  separate plant pigments.

Distillation : It is a type of separation process in which the mixture of liquid separated or evaporated at different temperatures.

Fractional distillation is separation of a liquid mixture into fractions which differ in boiling points by means of distillation by use of a fractionating column.

Filtration : It is a type of mechanical separation process in which the solid is separated from the liquid through the filter paper.

The kinetic molecular theory describes the solid state as composed of tightly packed particles that vibrate about fixed positions and are held together by strong intermolecular forces. This leads to solids having a defined shape and volume, and being less compressible compared to liquids and gases.

Solid State According to the Kinetic Molecular Theory

The kinetic molecular theory is a framework used to describe the behavior of matter in different states - solid, liquid, and gas. According to this theory, the solid state of matter is characterized by particles that are tightly packed together, often in a regular pattern. These particles have very little movement, primarily vibrating about fixed positions.

In the context of the kinetic molecular theory, intermolecular attractions are significant in the solid state, holding the particles closely to one another. This close packing and the limited movement of particles correspond to the low kinetic energy compared to gases. These properties explain why solids have a definite shape and volume, and why they are not easily compressible.

Focusing on the particles' behavior in solids, we understand that the restricted motion due to strong intermolecular forces results in the characteristic rigidity and structural stability of the solid state. Although the particles are in motion, it is minimal and does not allow for the particles to move past each other, unlike in liquids or gases.

to answer your second question, it is D

Answer. A. 183

B. 142

C. 0.03

D.11.3

E.24.5

Explanation:

The number of molecules present in 2.10 moles of CO₂ is 1.264×10²⁴ molecules. Therefore, option D is correct.

The mole is the amount of substance in a system that contains as many elementary entities as there are atoms in 0.012 kilogram of carbon 12; its symbol is "mol".

In the International System of Units, the mole (symbol mol) is the unit of substance amount (SI). The amount of substance is a measurement of how many elementary entities of a given substance are present in an object.

From Avogadro's hypothesis as follows;

1 mole of any substance = 6.023×10²³ molecules.

This implies that:

1 mole of CO₂ = 6.023×10²³ molecules

With the above information, we can obtain the number of molecules in 2.10 moles of CO₂. This can be obtained as given below:

1 mole of CO₂ = 6.023×10²³ molecules

Then,

2.10 moles of CO₂ = 2.10 × 6.02×10²³

2.10 moles of CO₂ = 1.264×10²⁴ molecules

Thus, the number of molecules present in 2.10 moles of CO₂ is 1.264×10²⁴ molecules., option D is correct.

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Answer: ΔH°f is not zero

Explanation:

the change in enthalpy formation is zero when elements are pure.when they are zero it is mainly  because they are most basic,where you cannot form an element with an element.

The partial pressure of Ne is [tex]\boxed{1.063{\text{ atm}}}[/tex].

Further Explanation:

Dalton’s law:

This law states that partial pressure of any gas is calculated by the multiplication of mole fraction and the total pressure of gas mixture.

The expression for partial pressure of a particular gas is,

[tex]{P_{{\text{gas}}}} = {X_{{\text{gas}}}} \cdot {P_{{\text{total}}}}[/tex]                                                                         …… (1)

Where,

[tex]{P_{\text{gas}[/tex] is the partial pressure of the gas.

[tex]{P_{{\text{total}}[/tex] is the total pressure of the mixture.

[tex]{X_{{\text{gas}}}[/tex] is the mole fraction of gas.

The formula to calculate moles of component is as follows:

[tex]{\text{Moles of component}} = \dfrac{{{\text{Mass of component}}}}{{{\text{Molar mass of component}}}}[/tex]                                   …… (2)

Substitute 10.0 g for mass of component and 20.179 g/mol for molar mass of component in equation (2) to calculate moles of Ne.

 [tex]\begin{aligned}{\text{Moles of Ne}} &= \frac{{{\text{10}}{\text{.0 g}}}}{{{\text{20}}{\text{.179 g/mol}}}} \\ &= 0.4956{\text{ mol}} \\\end{aligned}[/tex]

Substitute 10.0 g for mass of component and 39.948 g/mol for molar mass of component in equation (2) to calculate moles of Ar.

 [tex]\begin{aligned}{\text{Moles of Ar}} &= \frac{{{\text{10}}{\text{.0 g}}}}{{{\text{39}}{\text{.948 g/mol}}}} \\&= 0.2503{\text{ mol}} \\ \end{aligned}[/tex]

Total number of moles can be calculated as follows:

[tex]\begin{aligned}{\text{Total number of moles}} &= \left( {0.4956 + 0.2503} \right){\text{ mol}} \\ &= 0.7459{\text{ mol}} \\\end{aligned}[/tex]

The formula to calculate mole fraction of Ne is as follows:

[tex]{\text{Mole fraction of Ne}} = \dfrac{{{\text{Moles of Ne}}}}{{{\text{Total number of moles}}}}[/tex]                                    …… (3)

Substitute 0.4956 mol for moles of Ne and 0.7459 mol for total number of moles in equation (3).

[tex]\begin{aligned}{\text{Mole fraction of Ne}} &= \frac{{{\text{0}}{\text{.4956 mol}}}}{{{\text{0}}{\text{.7459 mol}}}} \\&= 0.6644 \\\end{aligned}[/tex]  

Substitute 0.6644 for [tex]{X_{{\text{gas}}}}[/tex] and 1.6 atm for [tex]{P_{{\text{total}}}}[/tex] in equation (1) to calculate partial pressure of Ne.

[tex]\begin{aligned}{P_{{\text{Ne}}}} &= \left( {0.6644} \right)\left( {1.6{\text{ atm}}} \right) \\&= 1.063{\text{ atm}} \\\end{aligned}[/tex]  

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Answer details:

Grade: Middle School

Subject: Chemistry

Chapter: Gases and the kinetic-molecular theory  

Keywords: partial pressure, mole fraction, Ne, Ar, moles, molar mass, mass, 1.063 atm, 1.6 atm, 0.6644, mole fraction of Ne.

Final answer:

To find the average atomic mass of weapons-grade uranium, calculate the weighted average based on the percentages of each isotope: 80% of 235.044 amu (uranium-235) and 20% of 238.051 amu (uranium-238), yielding an average atomic mass of 235.6454 amu.

Explanation:

To calculate the average atomic mass of weapons-grade uranium, which consists of 80% uranium-235 and 20% uranium-238, you multiply the mass of each isotope by its relative percentage (expressed as a decimal) and then sum the results. The atomic mass unit (amu) for uranium-235 is 235.044 and for uranium-238 is 238.051.

The average atomic mass can be calculated as follows:

(80% of uranium-235) 80/100 × 235.044 amu = 188.0352 amu

(20% of uranium-238) 20/100 × 238.051 amu = 47.6102 amu

Add these values together: 188.0352 amu + 47.6102 amu = 235.6454 amu

Therefore, the average atomic mass of weapons-grade uranium is 235.6454 amu.

The percent error for the 10 mL of water, given a measured mass of 9.925 g and a density of 0.9975 g/mL, is approximately 0.501%.

To calculate the percent error for the 10 mL of water given the measured mass and the density of water, we can use the formula for percent error:

Percent Error = | (Experimental Value - Theoretical Value) / Theoretical Value | × 100%

The theoretical mass of 10 mL of water using the density 0.9975 g/mL is calculated as follows:

Theoretical Mass = Volume × Density = 10 mL × 0.9975 g/mL = 9.975 g

The experimental mass measured is 9.925 g. Now, applying the percent error formula:

Percent Error = | (9.925 g - 9.975 g) / 9.975 g | × 100% = |(-0.05 g) / 9.975 g| × 100% ≈ 0.501%

Therefore, the percent error for the measurement of 10 mL of water is approximately 0.501%.

Answer : The correct option is, (a) 8.0 g

Solution : Given,

Percent of solute = 4 %

Mass of solution = 200 g

Mass by mass percent (m/m)% : It is defined as the mass of solute present in the mass of solution.

Formula used :

[tex](m/m)\%=\frac{\text{Mass of solute}}{\text{Mass of solution}}\times 100[/tex]

Now put all the given values in this formula, we get the mass of solute.

[tex]4\%=\frac{\text{Mass of solute}}{200g}\times 100[/tex]

[tex]\text{Mass of solute}=8.0g[/tex]

Therefore, the mass of solute in solution is, 8.0 g

The partial pressure of carbon dioxide (PCO2) in systemic arterial blood is approximately 40 mm Hg.

The partial pressure of a gas in a mixture, like blood, is a measure of the pressure that gas exerts independently, assuming ideal behavior. In the context of blood gases, PCO2 is a crucial parameter reflecting the concentration of dissolved carbon dioxide in the bloodstream.

Normal systemic arterial blood PCO2 levels typically range from 35 to 45 mm Hg. This range is maintained within a very narrow margin as part of the body's acid-base balance, regulated by the respiratory system and the kidneys.

A PCO2 value significantly higher than 45 mm Hg can indicate respiratory acidosis, a condition where the blood becomes too acidic due to excess carbon dioxide. On the other hand, a PCO2 value below 35 mm Hg may indicate respiratory alkalosis, where the blood becomes too alkaline due to insufficient carbon dioxide.

Therefore, a PCO2 of 100 mm Hg, 104 mm Hg, or 45 mm Hg does not represent the typical PCO2 in systemic arterial blood and would suggest an abnormal condition. A PCO2 of 40 mm Hg is within the normal range for systemic arterial blood PCO2.

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Answer:

cfcl2

Explanation:edg

Answer:

When we move across the period from left to right then there is decrease in atomic radius.

This is due to increase in number of protons and electrons across a period. Since electrons are added in same energy level, therefore, they get pulled closer to the nucleus because of more number of protons which carry a positive charge.

As a result, there is shrinkage in size from left to right across the period.

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Explanation:

The atomic radius increase as we move down the group in the periodic table because of the addition of a new principal shell.

The atomic radius of an atom can be described as the shortest distance between the nuclei of the atom and the valence shell of the atom. An atomic radius is also specified as half the distance between two adjacent atoms of the same element directly bonded in a molecule.

In general, the atomic radius of an atom increases when we move down a group on the modern periodic table. In groups in the periodic table, the addition of a new principle shell as we move down. Therefore the distance between the nucleus and the outermost shell increases and the electronegativity decreases and the atomic radius increases.

In periods in the periodic table, the electrons are in the same valence shell therefore the atomic number of elements increases within the same period. While moving from left to right, the effective nuclear charge increases.

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The correct answer is 2