Which of the following increases the rate of a chemical reaction?

A. Increasing the number of different elements involved in the reaction

B. Increasing the temperature of the materials reacting

C. Decreasing the concentration of the materials reacting

D. Decreasing the temperature of the materials reacting

Answer:

The correct answer is C.

Explanation:

Enzymes are proteins that catalyze chemical reactions in living things. Enzymes are catalysts, so they are substances that without being consumed in a reaction significantly increase the speed. They do not make impossible reactions feasible but accelerate those that could spontaneously occur, increasing their speed when reacting.

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Final answer:

The balanced net precipitation reaction for BaCl₂ and KOH results in solid barium hydroxide and potassium chloride in solution, with the net ionic equation being Ba²⁺(aq) + 2OH⁻(aq) → Ba(OH)₂(s)

The balanced net precipitation reaction between aqueous barium chloride (BaCl2) and potassium hydroxide (KOH) involves a double displacement reaction where the cation of one reactant (Ba2+ from BaCl2) combines with the anion of the other reactant (OH- from KOH) to form an insoluble product, barium hydroxide (Ba(OH)2).

The complete balanced equation is:
BaCl₂(aq) + 2KOH(aq) → Ba(OH)₂(s) + 2KCl(aq)

The net ionic equation, which shows only the species that change during the reaction, is:

Ba²⁺(aq) + 2OH⁻(aq) → Ba(OH)₂(s)

This equation is balanced both in terms of atoms and electric charge, with barium ions and hydroxide ions forming barium hydroxide, which precipitates out of the solution as a solid.

Final answer:

The balanced chemical equation for the decomposition of copper(II) nitrate into copper(II) oxide, nitrogen dioxide, and oxygen is 2 Cu(NO3)2 ➔ 2 CuO + 4 NO2 + O2. This illustrates the conservation of mass by ensuring equal numbers of each type of atom on both sides of the equation.

Explanation:

The question you've asked pertains to balancing the chemical equation Cu(NO3)2 ➔ CuO + NO2 + O2. This process involves ensuring that the number of atoms for each element is the same on both sides of the equation.

To balance this equation, we start with the given substances and adjust the coefficients (the numbers in front of the chemical formulas) to make sure the atoms are balanced. After several steps of balancing, we arrive at the balanced equation:

2 Cu(NO3)2 ➔ 2 CuO + 4 NO2 + O2

This equation indicates that 2 moles of copper(II) nitrate decompose to form 2 moles of copper(II) oxide, 4 moles of nitrogen dioxide, and 1 mole of oxygen gas. The balancing process takes into account the conservation of mass, which states that atoms are neither created nor destroyed in a chemical reaction.

The C3H8 sample has 2.82 x 1024 carbon atoms and a total mass of 68.8712 g.

Given that the number of H atoms in the C3H8 sample is 7.52 x 1024, calculating the number of propane (C3H8) molecules involves dividing that number by the amount of hydrogen atoms in a single C3H8 molecule, which is 8. This gives us the number of molecules in the sample as 9.4 x 1023 molecules.

As each propane molecule has 3 carbon atoms, the total amount of carbon atoms in the sample can be found by multiplying 9.4 x 1023 by 3, resulting in 2.82 x 1024 carbon atoms.

In order to find the total mass of the sample, we need to know the molar mass of propane, which is 44.097 g/mol. Using Avogadro's number (6.02 x 1023 molecules/mol), we can find the number of moles in the sample, which is 1.56 moles of propane. Multiplying this by the molar mass, we get that the total mass of the sample is 68.8712 g.

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Answer: atomists before Leucippus and Democritus described fire as being one of the four origins of matter, but Democritus and Leucippus described fire as being just likeeverything else and being composed of atoms.

Explanation:

1) Consider the following silica gel TLC plate of compounds A, B, and C developed in hexanes:

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2) You are trying to determine a TLC solvent system which will separate the compounds X, Y, and Z. You ran the compounds on a TLC plate using hexanes/ethyl acetate 95:5 as the eluting solvent and obtained the chromatogram below. How could you change the solvent system to give better separation of these three compounds?

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3) After a rather lengthy organic chemistry synthesis procedure, a student ran the product of the reaction on a TLC plate and obtained the result below. What might he/she have done wrong, if anything?

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4) A student spots an unknown sample on a TLC plate. After developing in hexanes/ethyl acetate 50:50, he/she saw a single spot with an Rf of 0.55. Does this indicate that the unknown material is a pure compound? What can be done to verify the purity of the sample?

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5) Consider a sample that is a mixture composed of biphenyl, benzoic acid, and benzyl alcohol. The sample is spotted on a TLC plate and developed in a hexanes/ethyl acetate solvent mixture. Predict the relative Rf values for the three compounds in the sample.

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6) Plate A, below, represents the TLC chromatogram of a compound run in hexanes. The same compound was then spotted on a large TLC plate and again run in hexanes. Which TLC plate, B, C, or D, correctly represents how far the compound would run on the longer plate?

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Back to TLC

Answer:

d

Explanation:

Answer: B. Coniferous forests

Explanation:

The coniferous forests are found in regions of Siberia and Canada. These forests exhibit climatic conditions which range from extremely cold winters, mild to extremely hot summers. Thus the living beings in these forests exhibit adaptations. The organisms which are in brown coat acquire a trait of white coat in winters due to adaptation. It helps the organism to remain insulated and mimic the color of the snow so that the organism remain hidden from the predators.

Answer is: Talking to plants may or may not help plants grow faster because the amount of water given was likely different for each group.

The scientific method is a process for experimentation that is used to explore observations.

Steps of the scientific method:

1) ask a question about something that is observed.

2) do background research. It this ecample, research is not good enough, because there are teo variables (talking to plants and amount of water).

3) construct a hypothesis, an attempt to answer questions with an explanation that can be tested.  

4) test of hypothesis.

5) analyze collected data and draw a conclusion.

Answer is: covalent.

Covalent compound (for example methane) are usually bad electricity and heat conductors, because molecules aren far from each other, so heat transfer is less efficient.

They do not form ions and atoms are less positive and negative than in ionic compounds.

Ionic compounds are good good electricity and heat conductors, because ionic compounds (for example sodium chloride NaCl) have mobile ions (cations and anions) that are able to transfer electrical charge. This compounds also conduct heat, because the ions are next to each other, so energy can be transferred efficiently from one place to another.

Answer:

C) Ionic bonds

Explanation:

The ionic bonds are the strongest bond, it occurs when a metal donates electrons and a nonmetal gain these electrons. They'll be together by electrostatic force.

Metallic bonds it the second strongest bond, it occurs between metals, which loses electrons. It's an electrostatic force, but weaker than the ionic compound because it occurs between the cation and the electron.

Covalent bonds are the weakest bond. It happens between metals and nonmetals, or nonmetals and hydrogen or between atoms of hydrogen. The force that joins the atoms depends on the polarity of the molecule. Polar molecules have dipole forces, nonpolar molecules, induced dipole forces. Also, hydrogen makes special dipole forces with nitrogen, oxygen, and fluorine, called hydrogen bond.

As the stronger is the force, as difficult it will be to break it. So, ionic bonds will demand more energy to become gas, and have high melting points.

Compounds with high melting points have [tex]\boxed{{\text{C}}{\text{. ionic bonds}}}[/tex].

Further Explanation:

The attraction between different atoms, molecules and ions is known as a chemical bond. Such bonds are responsible for the formation of chemical compounds.

Ionic bond

It is formed by the interaction of a metal with a non-metal. Metals are electropositive in nature so they have the tendency to lose electrons whereas non-metals tend to gain electrons due to their high electronegativity. Metal atoms form cations by loss of electrons and non-metals become anions with the gain of electrons.

Covalent bond

It is formed by the mutual sharing of electrons between the bonded atoms. It is also known as a molecular bond. Such bonds usually exist between two or more non-metals.

Metallic bonds

These are formed between metal atoms and metallic solids are produced. These are good conductors of electricity due to the presence of delocalized electrons. Copper, gold, zinc are examples of metallic solids.

An ionic bond is the strongest bond, followed by metallic bond and covalent bond is the weakest among the three given bonds. A large amount of energy is required to break ionic bonds as compared to the other two bonds so compounds with ionic bonds have high melting points. Therefore option C is correct.

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Answer details:

Grade: High School

Subject: Chemistry

Chapter: Ionic and covalent compounds

Keywords: chemical bond, melting points, metallic bond, ionic bond, covalent compound, interactions, metals, nonmetals, cations, anions, mutual sharing of electrons.

The decomposition of salt yielding a volatile product can increase the reported water content of a sample in volatilization gravimetry, due to the attribution of the mass loss of the volatile product to water content.

When a sample's salt decomposes, yielding a volatile product, the reported water content of the sample can be affected. In volatilization gravimetry, the sample undergoes thermal or chemical decomposition, which leads to a change in mass resultant from the loss of volatile material. If the decomposition of the salt generates a volatile product, such as water vapor, this will lead to an erroneously high water content measurement since the volatile product is included in the total mass loss that is attributed to water content.

The temperatures used in drying the sample affect the results. Drying the sample at a lower temperature (103-105°C) could result in the retention of some occluded water, whereas drying at a higher temperature (180°C) may release occluded water but also cause a greater loss of substances like carbonates. If salts like chlorides and nitrates decompose, they may form volatile products that could escape, thereby falsely increasing the measurement of the water content.

To ensure accurate evaluations, it's essential to understand the decomposition products and use specialized equipment to trap and weigh any volatile products. This allows for a more precise measurement of the true water content of the sample.

STM in science stands for Scanning Tunneling Microscope, a device that allows visualization of atomic-level details on surfaces, revealing individual atoms and contributing to nanotechnology research.

In science, STM refers to a Scanning Tunneling Microscope, an instrument for imaging surfaces at the atomic level. An STM uses a sharp tip that scans a surface at a constant potential. As the tip moves close to surface atoms, electrons tunnel from the surface to the tip, creating a current that varies based on the distance between the tip and the surface. This tunneling-electron current is monitored and used to construct an image of the specimen with atomic-scale resolution. With an STM, scientists can literally see individual atoms, such as those on a sheet of gold, and structures like carbon nanotubes, providing profound insights into the physical world at the nanoscale.