Which statement describes the periodic law?
Metals are both good conductors of heat and electricity.
Atomic masses always increase across a period.
Nonmetals are of the most reactive elements.
Elements in the same group have similar chemical properties.

Final answer:

To determine the mass of 0.40 mole of NaBH4, calculate the molar mass of NaBH4 and multiply by the number of moles, resulting in 15.136 grams.

Explanation:

To find out how many grams are in 0.40 mole of NaBH4, we need to first calculate the molar mass of NaBH4. This involves adding the atomic masses of sodium (Na), boron (B), and hydrogen (H). The atomic masses are 22.99 g/mol for Na, 10.81 g/mol for B, and 1.01 g/mol for each of the four hydrogen atoms, giving us:

Molar mass of NaBH4 = 22.99 + 10.81 + (4 × 1.01) = 37.84 g/mol.

Now we can calculate the mass by multiplying the number of moles by the molar mass:

Mass = 0.40 moles × 37.84 g/mol = 15.136 grams of NaBH4.

A weather map showing an advancing mass of cold air indicates the formation of a cold front with associated low pressure, resulting in rapid upward air movement, precipitation, and a significant drop in temperature and humidity after the front passes. Option D is correct.

Based on the weather map, the conditions that would be predicted involve an advancing mass of cold air that creates a cold front. This is typically associated with a low pressure area as the front approaches. The cold front often leads to a sudden change in weather, characterized by rapid upward movement of air.

This results in the formation of vertically-developed clouds such as cumulus and cumulonimbus, leading to intense, but short-lasting precipitation. After the cold front passes, there is usually a marked drop in temperature and humidity, along with a shift in wind direction from south or southwest to west or northwest.

Hence, D. is the correct option.

The complete question is:

What conditions would be predicted based on the information in the weather map?

A) The advancing mass of cold air creates a low pressure area.

B) The cold front advances without bringing any change in the weather.

C) The high pressure causes cold air to move toward the low pressure areas.

D) The cold front advances from an area of high temperature to an area of low pressure.

Diffusion of nonpolar molecules is does not affected by charge. Because they have no partial charges. Hence option d is correct.

Diffusion of substance is the spreading or transfer of compounds based on concentration gradient or pressure gradient. Molecules diffuses from higher concentration region to lower concentration region.

Non-polar molecules are those which have no permanent dipole moment. They have no partial charges formed during chemical bonding. Whereas, polar compounds are those having permanent dipole moment and are having partial charges.

All other factors, such as temperature, pressure, concentration and molecular size will affect the rate of diffusion. Thus for non-polar compounds charge is  affecting the diffusion.

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Your question is incomplete but your complete question probably was:

Diffusion of nonpolar molecules would not be affected by

a.molecule size.

b.steepness of the concentration gradient.

c.temperature.

d.charge.

e.steepness of the pressure gradient

Answer:

- Both of their valence electrons are at p subshell.

- They have the first subshell full of electrons.

- Both of them have just 1 electron at the last p subshell.

Explanation:

Hello,

In this case, we could understand their electron structures by identifying their electron configurations as shown below:

[tex]B^5\rightarrow 1s^2,2s^2,2p^1\\Al^{13}\rightarrow 1s^2,2s^2,2p^6,3s^2,3p^1[/tex]

In such a way, we could notice the following similarities:

- Both of their valence electrons are at p subshell.

- They have the first subshell full of electrons.

- Both of them have just 1 electron at the last p subshell.

Best regards.

Answer: Option (c) is the correct answer.

Explanation:

When current passes through a wire then a magnetic field is formed. Therefore, when two wires carry current in the same direction then both the wires with have respective magnetic fields in the same direction and their total magnetic field will be large.

But when current between two wires flow in opposite direction then the magnetic field produced will also be in opposite direction. Therefore, both the magnetic fields cancel each other out. Thus, total magnetic field will be small.

As a result, wires which carry current in the opposite direction repel each other.

Answer:

E = hf

Explanation:

A photon is a particle which represents a 'quantum of light' or other electromagnetic radiation. These are particles that carry no mass and move at the speed of light.

The energy of a photon (E) can be given by Planck's equation where:

[tex]E = hf[/tex]

h = planck's constant = 6.626 *10⁻³⁴ Js

f = frequency of photon = [tex]\frac{c}{\lambda }[/tex]

where λ = wavelength of photon.

Therefore, [tex]E= \frac{hc}{\lambda }[/tex]

The molar mass of an element is equal to the element's atomic weight mentioned in the periodic table.

Molar mass of a compound or a molecule is defined as the mass of the elements which are present in it.The molar mass is considered to be a bulk quantity not a molecular quantity. It is often an average of the of the masses at many instances.

The molecular mass and formula mass are used as synonym for the molar mass.It does not depend on the amount of substance which is present in the sample.It has units of gram/mole.

Molar masses of an element are given as relative atomic masses while that of compounds is the sum of relative atomic masses which are present in the compound.The element's molar mass is mentioned in the box of the element's symbol in the periodic table.

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Among the compounds NaNO2, KHSO4, KBr, and Ba(NO3)2, KHSO4 forms an acidic solution when dissolved in water. It can donate a proton, subsequently increasing the concentration of hydronium ions. The other compounds do not result in an increased concentration of hydronium ions and thus, do not form acidic solutions.

When you're determining which of these compounds--NaNO2, KHSO4, KBr, Ba(NO3)2--forms an acidic solution when dissolved in water, it's important to understand how compounds behave in water. Most notably, you should know that an acidic solution contains a greater concentration of hydronium ions (H3O+) than hydroxide ions (OH-).

Sulfuric acid is a diprotic acid, which means it can donate two protons. It forms both sulfates and hydrogen sulfates in solution, and most of these compounds moderate the pH when dissolved in water. Consequently, KHSO4 is the compound that will result in an acidic solution, since upon dissolution, it can donate a proton and thereby increase the concentration of H3O+ ions.

As a note, the other compounds listed (NaNO2, KBr, Ba(NO3)2) do not increase the concentration of H3O+ ions; thus, they won't form acidic solutions. For instance, Ba(NO3)2 in a neutralization reaction with water will form a neutral salt and water.

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The final volume of the balloon after adding oxygen is 21 L.

To find the new volume of the balloon after adding oxygen, we can use Avogadro's law, which states that at constant temperature and pressure, equal volumes of gases contain equal numbers of moles. Initially, the balloon is filled with 4.00 moles of hydrogen in a volume of 21 L. When 2.00 moles of oxygen are added, the total number of moles becomes 6.00 moles. Since the hydrogen and oxygen are now mixed together, their volumes must be equal, so the final volume of the balloon is also 21 L.

Final answer:

To calculate the equilibrium constant for the reaction NO− 2 (aq) + H2O(l) → HNO2(aq) + OH−(aq), reverse the first given reaction, H3O+ + NO− 2 → HNO2 + H2O with Kc = 3.86 × 10³, and divide by the autoionization constant of water, Kw = 1.0 × 10−14, to obtain Kc = 3.86 × 10³17.

Explanation:

To calculate the equilibrium constant (Kc) for the chemical reaction NO− 2 (aq) + H2O(l) → HNO2(aq) + OH−(aq), we need to use the given equilibrium constants for related reactions and the autoionization of water.

The first reaction is:

The second reaction is the autoionization of water:

By reversing the first reaction and dividing its Kc by Kw, we can obtain the equilibrium constant for the reaction NO− 2 (aq) + H2O(l) → HNO2(aq) + OH−(aq):

The number of particles in A is 1.506 x 10²³, in B is 5.156 x 10²⁰, in C is 2.131 x 10²⁵, and in D is 2.559 x 10²³.

To determine the number of particles in each of the following substances, it is required to use Avogadro's number, which is 6.022 x 10²³ particles per mole. We can use dimensional analysis, also known as the unit conversion method, to convert from moles to particles.

A. 0.250 mol silver

Number of particles = 0.250 mol x 6.022 x 10²³ particles/mol

Number of particles = 1.506 x 10²³ particles

B. 8.56 x 10⁻³ mol NaCl

Number of particles = 8.56 x 10⁻³ mol x 6.022 x 10²³ particles/mol

Number of particles = 5.156 x 10²⁰ particles

C. 35.4 mol CO₂

Number of particles = 35.4 mol x 6.022 x 10²³ particles/mol

Number of particles = 2.131 x 10²⁵ particles

D. 0.425 mol N₂

Number of particles = 0.425 mol x 6.022 x 10²³ particles/mol

Number of particles = 2.559 x 10²³ particles

Therefore, there are approximately 1.506 x 10²³ particles in 0.250 mol of silver, 5.156 x 10²⁰ particles in 8.56 x 10⁻³ mol of NaCl, 2.131 x 10²⁵ particles in 35.4 mol of CO₂, and 2.559 x 10²³ particles in 0.425 mol of N₂.

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Answer: The pH of the solution is 9.68

Explanation:

To calculate the molarity of solution, we use the equation:

[tex]\text{Molarity of the solution}=\frac{\text{Mass of solute}}{\text{Molar mass of solute}\times \text{Volume of solution (in L)}}[/tex]

We are given:

Mass of solute (barium hydroxide) = 4.02 mg = 0.00402 g   (Conversion factor:  1 g = 1000 mg)

Molar mass of barium hydroxide = 171.34 g/mol

Volume of solution = 1 L

Putting values in above equation, we get:

[tex]\text{Molarity of solution}=\frac{0.00402g}{171.34g/mol\times 1L}\\\\\text{Molarity of solution}=2.4\times 10^{-5}M[/tex]

To calculate the pH of the solution, we need to determine pOH of the solution. To calculate pOH of the solution, we use the equation:

[tex]pOH=-\log[OH^-][/tex]

On complete dissociation, 1 mole of barium hydroxide produces 2 moles of hydroxide ions

We are given:

[tex][OH^-]=4.8\times 10^{-5}M[/tex]

Putting values in above equation, we get:

[tex]pOH=-\log(4.8\times 10^{-5})\\\\pOH=4.32[/tex]

To calculate pH of the solution, we use the equation:

[tex]pH+pOH=14\\pH=14-4.32=9.68[/tex]

Hence, the pH of the solution is 9.68

Considering the definition of pH, pOH and strong base, the pH of a 4.02 mg/L Ba(OH)₂ solution is 9.67.

You have a  4.02 mg/L Ba(OH)₂ solution. Being the molar mass (that is, the mass of one mole of a substance, which can be an element or a compound.) of barium hydroxide 171.34 g/mole, and being 1 mg=0.001 g then, the amount of moles that contain 4.02 mg of Ba(OH)₂ can be calculated as:

[tex]4.02 mgx\frac{0.001 grams}{1 mg} x\frac{1 mole}{171.34 grams} =[/tex] 2.35×10⁻⁵ moles

Then, the concentration of the Ba(OH)₂ solution is 2.35×10⁻⁵[tex]\frac{moles}{L}[/tex]=2.35×10⁻⁵ M.

On the other side, a Strong Base is that base that in an aqueous solution completely dissociates into the cation and hydroxide ion.

In this case, Ba(OH)₂ is a strong base. Then, the dissociation reaction will be:

Ba(OH)₂ → Ba²⁺ + 2 OH⁻

Since Ba(OH)₂ will completely dissociate in water, you can observe that the concentration of OH⁻ will be twice the concentration of Ba(OH)₂.

So, [OH⁻]= 2×2.35×10⁻⁵ M

[OH⁻]= 4.7×10⁻⁵ M

pOH is a measure of hydroxyl ions in a solution and is expressed as the logarithm of the concentration of OH⁻ ions, with the sign changed:

pOH= - log [OH⁻]

So, in this case:

pOH= - log (4.7×10⁻⁵ M)

pOH= 4.33

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

The following relationship can be established between pH and pOH:

pH + pOH= 14

Being pOH= 4.33, pH is calculated as:

pH + 4.33= 14

pH= 14 - 4.33

pH= 9.67

Finally, the pH of a 4.02 mg/L Ba(OH)₂ solution is 9.67.

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Answer: The ratio of rate of effusion of helium and radon is 7.45

Explanation:

To calculate the rate of diffusion of gas, we use Graham's Law.

This law states that the rate of effusion or diffusion of gas is inversely proportional to the square root of the molar mass of the gas. The equation given by this law follows the equation:

[tex]\text{Rate of diffusion}\propto \frac{1}{\sqrt{\text{Molar mass of the gas}}}[/tex]

We are given:

Molar mass of Helium = 4.00 g/mol

Molar mass of Radon = 222.1 g/mol

Taking their ratios, we get:

[tex]\frac{Rate_{He}}{Rate_{Rn}}=\sqrt{\frac{M_{Rn}}{M_{He}}}[/tex]

[tex]\frac{Rate_{He}}{Rate_{Rn}}=\sqrt{\frac{222.1}{4.00}}\\\\\frac{Rate_{He}}{Rate_{Rn}}=7.45[/tex]

Hence, the ratio of rate of effusion of helium and radon is 7.45

The molarity of the diluted barium hydroxide solution is approximately 0.5018 M.

The molarity of the diluted solution is calculated by using the formula for molarity (M), which is:

[tex]\[ M = \frac{\text{moles of solute (n)}}{\text{volume of solution (V)}} \][/tex]

When a solution is diluted, the number of moles of solute remains constant. Therefore, we can equate the moles of solute in the concentrated solution to the moles of solute in the diluted solution:

[tex]\[ n_{\text{concentrated}} = n_{\text{diluted}} \][/tex]

Given that the molarity (M) is the number of moles of solute per liter of solution, we can write:

[tex]\[ M_{\text{concentrated}} \times V_{\text{concentrated}} = M_{\text{diluted}} \times V_{\text{diluted}} \][/tex]

We are given:

- [tex]\( M_{\text{concentrated}} = 3.41 \)[/tex] M (molarity of the concentrated barium hydroxide solution)

- [tex]\( V_{\text{concentrated}} = 41.0 \)[/tex] ml (volume of the concentrated solution, which we will convert to liters)

- [tex]\( V_{\text{diluted}} = 279 \)[/tex] ml (volume of the diluted solution, which we will also convert to liters)

First, we convert the volumes from milliliters to liters:

 [tex]\( V_{\text{concentrated}} = 41.0 \) ml \( = 41.0 \times 10^{-3} \) L\\ \( V_{\text{diluted}} = 279 \) ml \( = 279 \times 10^{-3} \) L[/tex]

Now we can solve for [tex]\( M_{\text{diluted}} \)[/tex]:

[tex]\[ M_{\text{diluted}} = \frac{M_{\text{concentrated}} \times V_{\text{concentrated}}}{V_{\text{diluted}}} \] \[ M_{\text{diluted}} = \frac{3.41 \times 41.0 \times 10^{-3}}{279 \times 10^{-3}} \] \[ M_{\text{diluted}} = \frac{3.41 \times 41.0}{279} \] \[ M_{\text{diluted}} = \frac{140.01}{279} \] \[ M_{\text{diluted}} \approx 0.5018 \text{ M} \][/tex]

The final temperature of the water : 30.506 °C

The law of conservation of energy can be applied to heat changes, i.e. the heat received / absorbed is the same as the heat released  

Qin = Qout  

Heat can be calculated using the formula:  

Q = mc∆T  

m = mass, g  

∆T = temperature difference, °C / K  

From reaction:  

2C₆H₆ (l) + 15O₂ (g) ⟶12CO₂ (g) + 6H₂O (l) +6542 kJ, heat released by +6542 kJ to burn 2 moles of C₆H₆

If there are 5.400 g of C₆H₆ then the number of moles:  

mol = mass: molar mass C₆H₆

mol = 5.4 : 78  

mol C₆H₆ = 0.0692

so the heat released in combustion 0.0692 mol C₆H₆:  

[tex]\rm Q=heat=\dfrac{0.0692}{2}\times 6542\:kJ\\\\Q=226.353\:kJ[/tex]

the heat produced from the burning is added to 5691 g of water at 21 C

So :

Q = m . c . ∆T (specific heat of water = 4,186 joules / gram ° C)  

226353 = 5691 . 4.186.∆T  

[tex]\rm \Delta T=\dfrac{226353}{5691\times 4.186}\\\\\Delta T=9.506\\\\\Delta T=T(final)-Ti(initial)\\\\9.506=T_f-21\\\\T_f=30.506\:C[/tex]  

the difference between temperature and heat  

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Specific heat  

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relationships among temperature, heat, and thermal energy.  

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When heat is added to a substance  

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Final answer:

A protein's structure is determined by its amino acid sequence, which is encoded by the DNA sequence of a gene. The DNA sequence is translated into a protein through a process involving transcription and translation, followed by folding of the amino acid chain into its final structure.

Explanation:

The structure of a protein is critical to its function, and this structure is determined by the sequence of amino acids that make up the protein. This sequence of amino acids is directly dictated by the DNA sequence of a gene.

The process of translating DNA information into the structure of a protein follows the Central Dogma of Molecular Biology, which entails the conversion of DNA code into RNA (transcription), and then RNA into a protein (translation). The amino acid sequence then folds into a three-dimensional structure, which is essential for the protein's function.

Key to understanding this process is recognizing that the DNA sequence is comprised of codons, groups of three nucleotides that correspond to specific amino acids.

Through the actions of ribosomes and transfer RNA molecules, these codons are read and the appropriate amino acids are assembled in the correct order, resulting in a polypeptide chain.

This chain then undergoes folding, sometimes with assistance from other proteins called chaperones, to achieve its final functional form.

Mendeleev left gaps in his periodic table predicting the discovery of unknown elements. These gaps ultimately validated the predictive power of the periodic table, as new elements were found that fitted these places which facilitated further advancements in chemistry and related fields.

Dmitri Mendeleev, a Russian chemist, organized the chemical elements into a table known as the periodic table. He left gaps in the table because he predicted that there were elements yet to be discovered that would fit into those spaces. Mendeleev even predicted some properties of these undiscovered elements based on their presumed placement on the table. His prediction was found to be extraordinary when later these gaps were filled by the discovery of elements like Gallium, Scandium, and Germanium.

The ultimate importance of these gaps can be found in the fact that it showed the predictive power of the periodic table. By having the elements arranged in such a way, it gave scientists a tool to predict and identify new elements, further expanding our understanding of the universe's atomic composition. This aspect of Mendeleev's periodic table has contributed significantly to the advancement of chemistry and related sciences.

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The molecular formula of the hydrocarbon is C4H8.

The molecular formula of the hydrocarbon can be determined using the given information. Since the compound is 82.66% carbon by mass, we can assume that the remaining percentage is hydrogen. The molar mass of the compound is 58.12 g/mol.

To find the molecular formula, we need to determine the empirical formula first. We assume 100 g of the compound, so 82.66 g is carbon and 17.34 g is hydrogen. Using the molar mass and the atomic masses of carbon and hydrogen, we can determine the moles of each element.

The empirical formula is CH2, and the molar mass of CH2 is 14.03 g/mol. To find the molecular formula, we divide the molar mass of the compound (58.12 g/mol) by the molar mass of CH2 (14.03 g/mol). The result is approximately 4.15. We round this to the nearest whole number, which gives us a molecular formula of C4H8.

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Ans: unstable isotopes

        source of thermal energy

        poses health problems

A nuclear power plant generates nuclear energy which is a non-renewable resource. Essentially a heavy unstable radioisotope splits in a nuclear reactor and generates large amounts of heat. Hence a nuclear power plant is a source of thermal energy.

The fissionable material in a reactors core is usually a radioisotope like Uranium(U-235). The splitting of the uranium nucleus also generates other radioactive fission products, which might leak into the surroundings in case of any accidents. Hence, nuclear reactors pose health problems.

Ionizing radiation can harm a person's health right away at large levels, and at very high doses, it can even result in radiation sickness and death. Ionizing radiation can have negative health effects at low levels, including cataracts, cardiovascular disease, and cancer. All the given options are correct.

Because the binding energy produced by a neutron's absorption is more than the critical energy needed for fission, uranium-235 is a fissile substance and fissions with low-energy thermal neutrons. Nuclear explosions, fast-neutron reactors, and thermal-neutron reactors can all be powered by fissile material.

The fuel that nuclear power plants most frequently use for nuclear fission is uranium. Even though uranium is a common metal found in rocks all over the world, it is regarded as a nonrenewable energy source. Because the atoms of a particular type of uranium, known as U-235, are simple to separate, nuclear power plants use it as fuel.

Inside a nuclear power plant's reactor, fission occurs. The core of the reactor is where the uranium fuel is located.

Thus the given options are correct.

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Answer: The average atomic mass of Strontium is 87.65 u

Explanation:

Average atomic mass of an element is defined as the sum of masses of each isotope each multiplied by their natural fractional abundance.

Formula used to calculate average atomic mass follows:

[tex]\text{Average atomcic mass }=\sum_{i=1}^n\text{(Atomic mass of an isotopes)}_i\times \text{(Fractional abundance})_i[/tex]     .....(1)

Mass of [tex]_{38}^{86}\textrm{Sr}[/tex] isotope = 85.91 u

Percentage abundance of [tex]_{38}^{86}\textrm{Sr}[/tex] isotope = 9.46 %

Fractional abundance of [tex]_{38}^{86}\textrm{Sr}[/tex] isotope = 0.09460

Mass of [tex]_{38}^{87}\textrm{Sr}[/tex] isotope = 86.91 u

Percentage abundance of [tex]_{38}^{87}\textrm{Sr}[/tex] isotope = 7.00 %

Fractional abundance of [tex]_{38}^{87}\textrm{Sr}[/tex] isotope = 0.0700

Mass of [tex]_{38}^{88}\textrm{Sr}[/tex] isotope = 87.91 u

Percentage abundance of [tex]_{38}^{88}\textrm{Sr}[/tex] isotope = 83.54 %

Fractional abundance of [tex]_{38}^{88}\textrm{Sr}[/tex] isotope = 0.8354

Putting values in equation 1, we get:

[tex]\text{Average atomic mass of Sr}=[(85.91\times 0.0946)+(86.91\times 0.0700)+(87.91\times 0.8354)][/tex]

[tex]\text{Average atomic mass of Sr}=87.65u[/tex]

Hence, the average atomic mass of Strontium is 87.65 u

Answer:

That it's excessively amazing, that with one present-day atomic vitality the earth as we probably are aware it could be decimated.  

I trust this makes a difference!

Explanation:

Answer:

Increasing the temperature Decreases the humidity and vice versa

Explanation:

When the temperature is increasing, the air can hold more water molecules ,thereby making the humidity to reduce. A high humidity will make the weather to be more hotter because the body sweat will not evaporate easily. A low humidity makes the weather cooler due to the fact the body sweat evaporate easily .