What are valence shell electrons

In a fuel cell, hydrogen and oxygen produce electrical energy through an electrochemical reaction, with high efficiency and low pollution. Direct combustion of hydrogen and oxygen, on the other hand, yields thermal energy with significant energy loss due to thermodynamic limitations.

The reaction of hydrogen and oxygen to produce energy in a fuel cell differs substantially from their interaction during the direct combustion of hydrogen and oxygen. In a fuel cell, hydrogen is oxidized at the anode, and oxygen is reduced at the cathode, which results in water as a byproduct and the production of electrical energy directly via an electrochemical reaction. This process is efficient, producing electricity with up to 50%-75% energy efficiency.

In contrast, the direct combustion of hydrogen and oxygen is a much less efficient process, as it generates energy in the form of heat through a combustion reaction. The energy released in direct combustion, when used to power a heat engine, succumbs to second-law thermodynamics constraints, resulting in at least half of the energy being "wasted" to the surroundings with only about 20%-25% energy efficiency.

Moreover, fuel cells are nonpolluting, significantly reduce greenhouse gas emissions, and contribute to less dependence on fossil fuels. However, challenges like economic viability and dependence on natural gas for hydrogen production still hinder the wide adoption of fuel cell technology for applications like fuel-cell vehicles (FCVs).

The pH of the substance is less than 6.8.

Phenol red is a pH indicator that changes color depending on the acidity or basicity of the solution it is added to. When phenol red is added to a solution, it exhibits a range of colors: it is yellow in acidic solutions (pH less than 6.8), red or pink in neutral solutions (pH around 6.8 to 8.2), and purple or red-violet in basic solutions (pH greater than 8.2). Since the phenol red turned yellow upon addition to the unknown substance, this indicates that the pH of the substance is less than 6.8, meaning it is acidic.

/the first one is the right one :)

hope i helped

The upper layer is usually described as much younger than the lower layer. Therefore, option (A) is correct.

An unconformity can be described as a break in the geologic rock and fossil record. Rock layers are deposited continuously over geologic time and give information about the past events that have happened on earth.

Certain events can cause rocks to be eroded and results in an interruption in the geologic record. The surface between two rock layers of different ages is a break in an unconformity and the geologic record.

There are three kinds of geologic unconformities which are nonconformities, disconformities, and angular unconformities. Nonconformity can be described as a surface between two layers of sedimentary rock, where the upper layer is much younger than the lower layer.

All the layers that are above and below the unconformable surface are known as sedimentary rocks. A disconformity can be described as a surface that divides young sedimentary rocks from much older, underlying metamorphic rocks.

Learn more about unconformity, here:

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Answer:

B

Explanation:

To get the answer, you must know first the formula:

We know that moles = mass divided by molecular weight

So to get the mass, we need to alter the original formula, so

mass of sodium = 1.5 moles x atomic weight of Na

so what is the atomic weight of Sodium? It is 22.989769 u.

so the mass of sodium = 1.5 moles x 22.989769 u = 34.4846535

Final answer:

The empirical formula of the compound containing 40.0% C, 6.71% H, and 53.28% O is C₁H₂O₂.

Explanation:

The empirical formula can be determined by calculating the molar amounts of carbon and hydrogen in the sample based on the masses of carbon dioxide and water produced. In this case, the sample contains 40.0% carbon, 6.71% hydrogen, and 53.28% oxygen. Assuming a 100 g sample, we would have 40.0 g of carbon, 6.71 g of hydrogen, and 53.28 g of oxygen. Converting these masses to moles using the molar masses of the elements (carbon: 12.01 g/mol, hydrogen: 1.008 g/mol, oxygen: 16.00 g/mol), we find that we have 3.3333 moles of carbon, 6.6683 moles of hydrogen, and 3.33 moles of oxygen. Dividing these values by the smallest mole value gives a ratio of 1:2. Therefore, the empirical formula of the compound is C₁H₂O₂.

Given information:

Distance (d) = 50 miles

To determine:

The effect on speed as time increases

Explanation:

Speed can be defined as the ratio of the distance (d) traveled to the time (t) taken to cover that distance

Speed = distance/time -----(1)

In the given example since the distance is fixed an increase in the time of the trip will increase the denominator in equation(1) thereby decreasing the speed.

Ans (B) It decreases

Answer:

BrF3

Explanation:

Find moles of Br2 and F2 with Pv=nrt formula , then, divide by smallest to find empirical formula

Answer:

The answer is lead (II) oxide.

Hope this helps you

Breaking an egg is an example of a physical change. This is because the egg was broken, thus its physical appearance was different. If you were to cook the egg, that would be a chemical change because that would result in a new chemical formation of the stuff inside of the egg. But since you're only breaking the egg, it's just a physical change.

I guess that answers both questions.

Hope that helped!

Answer:

Because the egg is broken in Physical Change.

Explanation:

Boiled Egg is inside the cooking rice in Chemical Change.

Final answer:

The limiting reagent is the reactant that is completely consumed and determines the amount of product formed in a chemical reaction.

Explanation:

The limiting reagent in a chemical reaction is the reactant that is completely consumed and determines the amount of product that can be formed. In the given equation a2+2b2→2ab2, we need to determine the limiting reagent. To do this, we compare the number of moles of each reactant to the coefficients in the balanced equation. The reactant that has fewer moles than required by the stoichiometry is the limiting reagent.

For example, if we have 2 moles of a2 and 3 moles of b2, we can see that a2 is in excess because it has more moles than required (2 moles versus 1 mole in the balanced equation). Therefore, b2 is the limiting reagent.

Answer : The number of atoms present are, [tex]6.3\times 10^{23}[/tex]

Explanation : Given,

Moles of [tex]CO_2[/tex] = 0.35 mole

As we know that, 1 mole of substance contains [tex]6.022\times 10^{23}[/tex] number of atoms.

In [tex]CO_2[/tex], there 1 atom of carbon and 2 atoms of oxygen. So, the total number of atoms in [tex]CO_2[/tex] are, 3.

As, 1 mole of [tex]CO_2[/tex] contains [tex]3\times 6.022\times 10^{23}[/tex] number of atoms.

So, 0.35 mole of [tex]CO_2[/tex] contains [tex]0.35\times 3\times 6.022\times 10^{23}=6.3\times 10^{23}[/tex] number of atoms.

Therefore, the number of atoms present are, [tex]6.3\times 10^{23}[/tex]

Final answer:

The melting point of H₂O at 0°C is the same as its freezing point, allowing solid and liquid water to coexist at this temperature due to the unique properties of how water molecules arrange themselves.

Explanation:

The melting point of H₂O, or water, is 0 degrees Celsius (0°C), which is crucially the temperature where both the solid and liquid forms of water can coexist in equilibrium. This means that at 0°C, water can either freeze or melt without a change in temperature.

Understanding this concept is important because it highlights the uniqueness of water and many of its properties, including its density. Ice, being the solid form of H₂O, is actually less dense than liquid water due to the way hydrogen bonds expand the molecular structure when freezing.

This property of water is essential for the environment and plays a pivotal role in the Earth's climate and helps sustain life.

Answer:

sodium hydroxide is solute and water is solvent

Explanation:

Answer : The correct option is, Light absorption

Explanation :

Microspectrophotometer : It is a type of instrument that measures the spectra of the microscopic sample by using the different wavelengths of an electromagnetic radiation.

It is designed to measure the the spectrum of the microscopic sample. It is also measure the transmittance, absorbance, polarization and fluorescence of the microscopic sample.

From the given options, the option light absorption is the correct option.

Hence, a microspectrophotometer measures the light absorption.

Answer:

Light absorption

Explanation: