How properties before and after a chemical reaction can be used to determine if a chemical reaction occurred

Answer:

C. smiling when you're happy

Explanation:

SInce it's just an emotion and isn't actually that nessary

Using the first law of thermodynamics, the change in internal energy of the system, given the work done on the system and the heat released by the system, was calculated to be -2.28 × 10^6 Joules.

The subject of this problem is a classic concept in thermodynamics: the conservation of energy. According to the first law of thermodynamics, the change in the internal energy (ΔU) of a system is the sum of the heat (Q) added to the system and the work (W) done on the system, expressed in the equation ΔU = Q - W.

In this case, the work is performed on the system, amounting to 425 kcal. To convert this into a common unit like Joules, use the conversion factor 1 kcal = 4.184 × 10^3 J. Therefore, the work done on the system (W) is 425 kcal × (4.184 × 10^3 J/kcal) = 1.78 × 10^6 J.

The heat released by the system (Q) is - 5.00 × 10^2 kJ (the negative sign indicates heat is lost from the system). Converting into Joules gives -5.00 × 10^2 kJ × (10^3 J/kJ) = -5.00 × 10^5 J.

Substituting Q and W into the equation gives ΔU = (-5.00 × 10^5 J) - (1.78 × 10^6 J) = -2.28 × 10^6 J. Hence, the change in internal energy of the system is -2.28 × 10^6 J.

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The change in internal energy of the system is -1277.4 kJ.

The change in internal energy of a system can be calculated using the equation:

Change in internal energy = heat transfer - work done

In the given scenario, the system receives 425 kcal of work and releases 5.00 × 102 kJ of heat. To calculate the change in internal energy, we need to convert the units to a consistent format. 1 kcal = 4.184 kJ, so the work done is 425 kcal x 4.184 kJ/kcal = 1777.4 kJ.

Using the formula, the change in internal energy is:

Change in internal energy = 5.00 × 102 kJ - 3 kJ = -1277.4 kJ

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A plant extract is a mixture due to the fact that it contains multiple compounds physically combined, they retain their individual characteristics. This makes the composition of extracts heterogeneous. Mixtures in the form of plant extracts are especially important in pharmaceutical science.

A plant extract is considered a mixture due to the fact that it contains multiple compounds physically combined, not chemically bonded. These compounds usually include various elements of the plant like oils, pigments, and other organic molecules, all present in varying amounts. The plant extract retains the characteristics of its individual components because they are not chemically reacting with one another, but simply mixed together, making it a heterogeneous mixture, as the same drop of the extract might have different compounds in different proportions.

This is not much unlike the example of an Italian dressing, where in different parts of the mixture you may find more oil or vinegar or herbs because the ingredients separate and settle unevenly throughout the mixture. Similarly, in a plant extract, the compounds will not be proportionately arranged in every drop of the mixture.

Particularly in pharmaceutical science, this heterogeneous nature is an advantage as different plants contain unique combinations of beneficial compounds. Examples include medicines such as aspirin and codeine, which were once derived from plant extracts. This demonstrates the importance of mixtures in medicinal applications.

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Answer: The number of molecules present in given amount of water are [tex]1.54\times 10^{23}[/tex]

Explanation:

To calculate the number of moles, we use the equation:

[tex]\text{Number of moles}=\frac{\text{Given mass}}{\text{Molar mass}}[/tex]

Given mass of water = 4.6 g

Molar mass of water = 18.0 g/mol

Putting values in above equation, we get:

[tex]\text{Moles of water}=\frac{4.6g}{18.0g/mol}=0.255mol[/tex]

According to mole concept:

1 mole of a compound contains [tex]6.022\time 10^{23}[/tex] number of molecules.

So, 0.255 moles of water will contain [tex]0.255\times 6.022\times 10^{23}=1.54\times 10^{23}[/tex] number of molecules.

Hence, the number of molecules present in given amount of water are [tex]1.54\times 10^{23}[/tex]

Answer:

faster.

Explanation:

Particles of water in the gas coming out of a pot of boiling water are moving faster than particles of water in the pot.

This is because the heat energy makes the molecules move faster, so the molecules "trapped" in the liquid are able to gradually break down the barriers of the liquid-air interface and, therefore, the amount of water. it decreases until it "disappears". When you boil water, that smoke you see coming out is nothing more than a bunch of molecules that have broken through the barrier and are free, gaseous. This was due to the rapid movement of these molecules.

We want to see what happens to the particle's speed in a given material as the temperature changes (increases in this case) and it faces a change of phase.

We will see that the particles in the gas (vapor of water) have a larger speed than the ones in the liquid water.

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To see this, first, we need to understand how the temperature manifests in a given material.

As we increase the temperature of the material, the kinetic energy of the particles that make the material increase (thus the speed increases). This causes the particles to move more, and this is why as we increase the temperature, is likely to see an increase in the volume.

This is the reason of why we usually see that a solid has less volume than a liquid, and a liquid has less volume than a gas (for the same mass of the same material).

Then as we increase the temperature of liquid water and that water starts to change of phase (by boiling) the kinetic energy of the particles increase, and thus, the speed increases.

Then the particles will be moving faster than the particles of the water in the pan.

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Final answer:

To find the volume of 2.00 moles of hydrogen gas at STP, multiply the number of moles by the standard molar volume, 22.4 L/mol, resulting in 44.8 liters.

Explanation:

The volume of hydrogen gas at STP (Standard Temperature and Pressure) can be found using the standard molar volume. By definition, the standard molar volume of an ideal gas at STP, which is 0°C (273 K) and 1 atm pressure, is 22.4 liters per mole.

For 2.00 moles of hydrogen gas at STP, the calculation simply involves multiplying the number of moles by the standard molar volume:

Thus, 2.00 moles of hydrogen gas at STP occupy a volume of 44.8 liters.

Answer: it would be erosions

Explanation:

The natural process most likely caused the valley to canyon is tectonic uplift and erosion.

Tectonic uplift is defined as the portion of the total geologic uplift to the mean of the earth surface that is not attributable to an isostatic response to an unloading.

Tectonic plate is defined as a scientific theory explaining how large landforms are formed as a result of subsurface motions on Earth.

Erosion is defined as the geological process in which earthen materials will move away and  transported by the natural force such as wind and water.    

There are basically two types of erosion

Thus, the natural process most likely caused the valley to canyon is tectonic uplift and erosion.

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The Nuclear Model-1909

Answer: Option A

Explanation:

The osmosis can be defined as a biological process where the movement of the particles takes place through the semipermeable membrane.The solvent moves from a region of high concentration to low concentration.

The diffusion is same in the reference that it can also occur through the semipermeable membrane.

The particles from the higher concentration moves towards the lower concentration.

Hence, option A is correct.

Answer: B- molecule

Explanation:

An atom is the smallest entity of a substance which may or may not have independent existence.

Molecule is a pure substance which is composed of similar kind of  atoms.It can not be decomposed into simpler constituents using chemical reactions.Example: Hydrogen [tex]H_2[/tex]

Compound is a pure substance which is made from atoms of different elements combined together in a fixed ratio by mass.It can be decomposed into simpler constituents using chemical reactions. Example: water [tex]H_2O[/tex]

Graphene is a crystalline allotrope of carbon and thus is a molecule as it is made up of  similar kind of  atoms.

Answer:

The correct answer is number 2: herbicides can increase crop yields by killing weeds.

Explanation:

Herbicides are chemiclas used to avoid the spreding of undesired plants (weeds) on crops. These weeds would be prejudicial to the harvest, therefore, herbicide use can increase crop yields.

Answer:

The independent variable controls the dependent variable.

Explanation:

Final answer:

In K2HPO4, the ions present are potassium ions (K+) and hydrogen phosphate ions (HPO42-). Hydrogen phosphate can further dissociate, but the dissociation leading to the formation of PO43- is much less due to the small value of the equilibrium constant. Hence, the solution is basic.

Explanation:

To identify the ions present in K2HPO4, we first consider the fact that K2HPO4 is a salt derived from the reaction of a strong base (KOH) with a weak acid (H3PO4), and it is made up of potassium ions (K+) and hydrogen phosphate ions (HPO42-). In aqueous solution, K2HPO4 fully dissociates into these ions:

K2HPO4 (s) → 2 K+ (aq) + HPO42- (aq)

The potassium ions, K+, are the cationic species and the HPO42- ions are the anionic species. The hydrogen phosphate ion is an amphiprotic species, meaning it can act as both an acid and a base. This ion may further dissociate in water:

First ionization: H2PO4- (aq) → H+ (aq) + HPO42- (aq)

Second ionization: HPO42- (aq) + H2O(l) ⇌ H3O+ (aq) + PO43- (aq)

However, the second ionization, which forms PO43- and H3O+, has an equilibrium constant (K2), which is much less than that of the first ionization, indicating that it occurs to a significantly lesser extent. The solution of K2HPO4 is basic because the K2 of the HPO42- ion is much larger than the acidic dissociation constant.

Radioactive isotope, also called radioisotope, radionuclide, or radioactive nuclide, any of several species of the same chemical element with different masses whose nuclei are unstable and dissipate excess energy by spontaneously emitting radiation in the form of alpha, beta, and gamma rays.

Answer:

Less stable

Explanation:

I took the K12 test

Answer:5

Explanation:

5

Copper, sulfur, gold, iron, and aluminum are elements, as their symbols suggest. The other four substances are compound with two elements each.

The maximum number of electrons that can occupy the principal quantum number 5 is 50, calculated using the formula 2n² where n is the principal quantum number.

The maximum number of electrons that can occupy the fifth energy level (n = 5) of an atom is determined by the formula 2n2. For n = 5, this formula gives:

2 × 52 = 2 × 25 = 50 electrons

Therefore, the maximum number of electrons that can occupy the principal quantum number 5 is 50. This includes the possible subshells in that energy level: 5s, 5p, 5d, and 5f, with the number of orbitals in each subshell being one s-orbital, three p-orbitals, five d-orbitals, and seven f-orbitals, respectively.