Chemistry help needed !!

Answer:

Cooling a substance causes molecules to slow down and get slightly closer together, occupying a smaller volume that results in an increase in density. Hot water is less dense and will float on room-temperature water. Cold water is dense and will sink in room-temperature water.

Explanation:

A: 1000 µL micropipette, B: 100 µL micropipette, C: 1000 µL micropipette or 1 mL graduated pipette and D: 20 µL micropipette or 25 µL micropipette.

A) 874 µL: An appropriate pipette to use for 874 µL could be a P1000 pipette, which has a volume range of 100 µL to 1000 µL.

B) 57 µL: An appropriate pipette to use for 57 µL could be a P200 or P20 pipette. The P200 has a volume range of 20 µL to 200 µL, while the P20 has a volume range of 2 µL to 20 µL.

C) 340 µL: An appropriate pipette to use for 340 µL could be a P1000 or P200 pipette.

D) 15 µL: An appropriate pipette to use for 15 µL could be a P20 pipette, which has a volume range of 2 µL to 20 µL.

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According to the kinetic-molecular theory, particles in solids are in constant motion.

Explain kinetic-molecular theory?

The kinetic-molecular theory is a theory that explains the properties of gases in terms of the motion and interactions of molecules. This theory states that all gases are composed of tiny particles that are in constant motion and that these particles collide with each other and with the walls of their container. The collisions between the molecules cause the gas particles to move in random directions, and the motion of these particles is what is responsible for the pressure of the gas. The kinetic-molecular theory also states that the average kinetic energy of the individual gas molecules is proportional to the temperature of the gas.

In the kinetic-molecular theory, particles in solids have fixed positions and are unable to move or vibrate, which help to explain the properties of solids such as their rigidity and strength.

Therefore, particles in solids are in constant motion.

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False. The specific heat at constant volume of a particular gas, at room temperature, is dependent not only on its molecular mass but also on the number of atoms and molecules in the gas.

Different gases have different molecular masses, and the specific heat at constant volume for a particular gas is therefore not fixed.

For example, the molecular mass of oxygen is 32 g/mol, but its specific heat at constant volume is 0.214 kcal/kg⋅K at room temperature, while nitrogen has a molecular mass of 28 g/mol and a specific heat at constant volume of 0.241 kcal/kg⋅K.

Therefore, the statement that the specific heat at constant volume of a particular gas is 0.182 kcal/kg⋅K at room temperature, and its molecular mass is 34 is false.

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All of this is summed up with the formula: Percentage Error is equal  ((Estimated Number – Actual Number)/ Actual number) x 100.

Depending on how close to the true value a measurement is, it may be accurate or inaccurate. Imagine you are conducting an experiment to find out how dense a sample of aluminum metal is. The true or accurate value of a measurement is one that is based on widespread agreement with an authoritative reference.

The accepted density for aluminum is 2.70g/cm3. A measurement's experimental value is its value as it is observed during the experiment. Let's say your experiment yields the experimental result that the aluminum density is 2.42g/cm3. The discrepancy between experimental and accepted values is an experiment's error.

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C₂H₂ is a nonpolar molecule.

Acetylene, commonly referred to as ethyne, is an organic chemical substance with the formula C₂H₂. This substance is a hydrocarbon since its entire atomic structure consists of hydrogen and carbon.

This is because the two carbon atoms form a triple bond with each other, and the two hydrogen atoms form single bonds with the carbon atoms. The electronegativity difference between carbon and hydrogen is very small, so the bonds are considered nonpolar.

Additionally, the molecule has a linear shape, which means that the charge distribution is symmetrical and there is no overall polarity. Therefore, C₂H₂ is a nonpolar molecule.

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Yes, methanol is a polar liquid.

Methanol is a simple alcohol consisting of a single carbon atom, three hydrogen atoms, and one hydroxyl group (-OH). The oxygen atom in the hydroxyl group is highly electronegative, meaning it attracts electrons towards itself. As a result, there is an uneven distribution of electron density in the molecule, with the oxygen end being slightly negative and the carbon end being slightly positive.

This polarity makes methanol a polar solvent, meaning it has the ability to dissolve polar substances. Polar substances, such as salts and sugars, are typically composed of atoms with high electronegativity differences, and they are attracted to the polar regions of methanol molecules.

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Answer:

The reaction between a conjugated diene and an alkene

Explanation:

The Diels–Alder reaction is the reaction between a conjugated diene and an alkene (dienophile) to form unsaturated six-membered rings. Since the reaction involves the formation of a cyclic product via a cyclic transition state, it is also referred to as a "cycloaddition".

The concentration of HCl in the solution is 0.651 mol/kg.

To find the concentration of Cl- ions in the CaCl2 solution, we can first calculate the number of moles of CaCl2 that were dissolved:

23.7 g of CaCl2 / 110.98 g/mol

=> 0.214 moles of CaCl2

Next, we can use the number of moles to find the number of moles of Cl- ions:

0.214 moles of CaCl2 × 2 moles of Cl- ions/mole of CaCl2

= 0.428 moles of Cl- ions

Finally, we can use the volume of the solution to find the concentration in moles per liter (M):

Volume = 375 g of water ÷ 1.05 g/mL

=> 357.14 mL

=> 0.35714 L

Concentration = 0.428 moles of Cl- ions ÷ 0.35714 L

=> 1.20 M

So, the concentration of Cl- ions in the CaCl2 solution is 1.20 M.

Next, to find the concentration of HCl in molality, we can first calculate the number of moles of HCl that were dissolved:

5.5 g of HCl ÷ 36.46 g/mol

=> 0.151 moles of HCl

Next, we can use the number of moles of HCl and the mass of the solvent (C2H6O) to find the molality:

Molality = 0.151 moles of HCl / (200 g of C2H6O ÷ 46.07 g/mol)

=> 0.651 mol/kg

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The pressure exerted by a gas can be calculated using the ideal gas law, which states that PV = nRT, where P is pressure, V is volume, n is the number of moles, R is the gas constant, and T is the temperature in kelvins.

Plugging in the given values, we get:

P = (nRT) / V

P = (1.35 mol * 8.31 J/mol*K * 320.0 K) / (2.50 L * 10^-3 m^3)

P = (4460.8 J) / (0.0025 m^3)

P = 17843.2 Pa

To convert from pascals to atmospheres, we divide by 101325 Pa/atm:

P = 17843.2 Pa / 101325 Pa/atm

P = 0.176 atm

So, the pressure exerted by 2.50 L of HF containing 1.35 mol at 320.0 K is approximately 0.176 atm.

The molecular weight is the number of grams per mole for the substance and the conversion factor for moles to grams for that specific substance.

Molecules are made up of different atoms. For example, a water molecule (H₂O) is composed of one oxygen atom and two hydrogen atoms. Molecular weight (or molecular weight) is the sum of the atomic masses of all atoms present in a molecule. Moles is the amount in grams of a substance numerically equal to molecular weight. According to Avogadro's number, the number of molecules of a substance in one mole is 6.02 × 10²³ molecules. If we know the molecular weight of a substance and number of moles, then we can calculate the weight of substance, using the formula: molecular weight × number of moles

= mass of the substance in grams. Therefore, the mass of 1 mole of water is 18.02 g (1 mole of H₂O x 18.02 g/mol = 18.02 g).Hence, we got the relationship between moles and mass of substance.

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The gauge pressure of the air in the tank is 101325 Pa - 9.439*L  when The air pressure in a tank is measured using an inclined manometer whose arm is inclined 45 degree.

Let's call the length of the inclined arm of the manometer L. Then, the vertical component of the arm length is given by

[tex]L sin(45) = L/\sqrt2[/tex]

Next, we can use the hydrostatic pressure equation to relate the pressure difference between the two arms of the manometer to the difference in height:

ΔP = ρgh

Where ΔP is the pressure difference, ρ is the density of the fluid, g is the acceleration due to gravity, and h is the difference in height between the two arms of the manometer.

Since the two arms of the manometer are open to the atmosphere, the pressure at the top of the manometer is equal to the atmospheric pressure, which we can assume to be 101325 Pa. Therefore, the gauge pressure of the air in the tank is equal to:

[tex]P_{gauge} = P_{atm} - \triangle P[/tex]

where [tex]P_{atm[/tex] is the atmospheric pressure.

Putting it all together, we get:

ΔP = (ρwater - ρair)gh

[tex]= (1000 kg/m^3 - 1.225 kg/m^3) * 9.81 m/s^2 * (L/\sqrt2)[/tex]

= 9.439 * L

Therefore, the gauge pressure of the air in the tank is:

Pgauge = Patm - ΔP

= 101325 Pa - 9.439 * L

Note that the pressure will be in Pa, and you can convert it to other units like psi or bar as necessary.

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The molecularity of an elementary reaction is equal to the sum of the stoichiometric coefficients of the reactants.

The molecularity of an elementary reaction is the number of molecules or atoms involved in the reaction. It is equal to the sum of the stoichiometric coefficients of the reactants.

(a) The elementary reaction Cl2(g) → 2 Cl(g) is a unimolecular reaction, as only one molecule is involved. The rate law for this reaction can be written as:

rate = k[Cl2]

(b) The elementary reaction OCl–(aq) + H2O(l) → HOCl(aq) + OH–(aq) is a bimolecular reaction, as two molecules are involved. The rate law for this reaction can be written as:

rate = k[OCl–][H2O]

(c) The elementary reaction NO(g) + Cl2(g) → NOCl2(g) is a bimolecular reaction, as two molecules are involved. The rate law for this reaction can be written as:

rate = k[NO][Cl2]

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When benzoic acid is treated with aqueous sodium hydroxide, it undergoes a neutralization reaction to form sodium benzoate, water, and hydrogen gas.

The balanced chemical equation for the reaction is: C6H5COOH + NaOH → C6H5COO-Na+ + H2O

In this reaction, the sodium hydroxide reacts with the benzoic acid to form sodium benzoate (the conjugate base of benzoic acid) and water.

The hydrogen gas is formed as a byproduct of the neutralization reaction. Sodium benzoate is completely soluble in water, while benzoic acid has limited solubility in water.

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The smallest component of an element that maintains its identity during a chemical reaction is known as the atom.

The smallest piece of matter with all of an element's chemical properties is an atom. The tiniest part of an element, an atom nonetheless possesses all of the element's chemical characteristics. is a positively charged particle that moves around the nucleus.

The smallest elemental particle that can retain all of an element's chemical characteristics is an atom. It is the indivisible unit of matter that is capable of existing alone. It is a substance that makes up matter. The smallest component of an element that maintains its identity during a chemical reaction is known as the atom.

The smallest component of an element, an atom has exactly the same chemical makeup as the element as a whole. Dalton's Atomic Theory, which states that all matter is made up of indivisible, indestructible atoms, was the first reliable theory describing the nature of matter.

Therefore, the correct answer is option C) atom.

The complete question is;

The smallest part of an element that retains the chemical properties of the element.

A) electron

B) molecule

C) atom

D) proton

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A shielded nucleus will have a reduced chemical shift and will absorb upfield from a deshielded nucleus.

The nucleus is the central part of an atom that contains most of its mass and all of its positive charge. It is composed of protons and neutrons, which are held together by a strong nuclear force. The number of protons in the nucleus determines the element that the atom belongs to, while the number of neutrons can vary and give rise to different isotopes of the same element. The properties of the nucleus are essential in determining the behavior of the atom in chemical and physical reactions. Nuclei can also undergo nuclear reactions such as fission and fusion, which release enormous amounts of energy and are the basis for nuclear power and nuclear weapons. The study of nuclei and their properties is known as nuclear physics and is a fundamental area of modern science.

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The given statement "when combining a strong acid with water to dilute it, you should add the acid to the water" is true because when diluting a strong acid, it is generally recommended to add the acid to the water, rather than the other way around; therefore the given statement is true.

This is because the process of mixing a strong acid with water can generate a significant amount of heat, and adding water to the acid can result in a rapid release of this heat, potentially causing the solution to boil or splatter. On the other hand, adding the acid slowly to the water allows for better heat dissipation, reducing the risk of splattering or boiling. Therefore, the general rule of thumb is to "add acid to water", which helps ensure safe and controlled mixing.

"

when combining a strong acid with water to dilute it, you should add the acid to the water.

True

False

"

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The size of filter paper you should use with a Hirsch funnel depends on the size of the funnel. if you have a Hirsch funnel with a diameter of 7cm, you might choose filter paper with a diameter of 9cm.

To determine the appropriate filter paper size, you should select a filter paper that is slightly larger in diameter than the widest part of the Hirsch funnel. This allows the filter paper to fit snugly in the funnel and helps to prevent it from folding or collapsing during the filtration process.

For example, if you have a Hirsch funnel with a diameter of 7 centimeters, you might choose filter paper with a diameter of 9 centimeters. This will provide enough excess filter paper to fold over the edges of the funnel and ensure a tight fit.

It's also important to choose the appropriate grade of filter paper based on the nature of the material being filtered and the desired filtration rate. You can consult the manufacturer's instructions or a laboratory handbook for guidance on selecting the appropriate grade of filter paper.

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MgBr2 will break down as 3 ions into in water

Describe an ion.

A charged atom or molecule is known as an ion. Because there are more electrons than protons in the atom or molecule, it is charged. Depending on whether the number of electrons in an atom is greater or less than the number of protons in the atom, an atom can develop a positive charge or a negative charge.

The ionic compound known as magnesium bromide is created when the metal magnesium and the non-metal bromine are combined. Each molecule of MgBr2 contains three ions (1x Mg2 and 2x Br-).

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The combustion reaction for propane can be represented as follows:

C3H8 (g) + 5O2 (g) → 3CO2 (g) + 4H2O (l)

The combustion reaction for gasoline (2,2,4-trimethylpentane) can be represented as follows:

C8H18 (g) + 25/2 O2 (g) → 8CO2 (g) + 9H2O (l)

In general, both types of engines produce CO2 and H2O as products of combustion. However, gasoline releases more CO2 per unit of fuel burned compared to propane, due to its higher carbon content. So, a car burning gasoline would produce more emissions of CO2 compared to a car burning propane.

There are 7 moles of co2(g) present in the vessel at equilibrium.

What is moles ?

A mole is the atom's elementary particle, an ion. The mole of the substance is always related to the Avogadro number. The mole is always associated with the weight or mass of the element or substance. The standard unit of a mole is mol. The mole is a significant factor of the reactant and products to form an equation. A mole calculates the atom, ion, and substance weighs.

What is equilibrium ?

A static or dynamic balance between opposing forces or actions, as in the case of a force acting on a body whose resultant is zero or of a reversible chemical process where the velocities in both directions are equal: a condition of intellectual or emotional balance.

Therefore, There are 7 moles of co2(g) present in the vessel at equilibrium.

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The polyester that gets formed in the reaction between ethylene glycol and phthalic anhydride is Glyptal.

Poly(ethylene terephthalate), additionally referred to as PET, is the main polyester. It is a copolymer of ethylene glycol and terephthalic acid. PET and all different polyesters are produced industrially with the aid of using transesterification reactions. PET is ready with the aid of using the response of dimethyl terephthalate with ethylene glycol at 150 °C. Glyptal is a polyester, is shaped with the aid of using ethylene glycol and phthalic acid shaped with the aid of using step-boom polymerization as proven withinside the above response. As it warms, the phthalic anhydride will start to soften and dissolve withinside the ethylene glycol. You may also note that because it does so, the answer seems to boil; the water produced with the aid of using the response is boiling away.

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In a chemical change, the substances that make up matter change into other substances with physical properties and chemical properties.

Chemical changes occur when a substance combines with another to form a new substance, called chemical synthesis or, alternatively, chemical decomposition into two or more different substances. These processes are called chemical reactions and, in general, are not reversible except by further chemical reactions. Some reactions produce heat and are called exothermic reactions and others may require heat to enable the reaction to occur, which are called endothermic reactions. Understanding chemical changes is a major part of the science of chemistry.

When chemical reactions occur, the atoms are rearranged and the reaction is accompanied by an energy change as new products are generated. An example of a chemical change is the reaction between sodium and water to produce sodium hydroxide and hydrogen. So much energy is released that the hydrogen gas released spontaneously burns in the air. This is an example of a chemical change because the end products are chemically different from the substances before the chemical reaction.

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Answer:

natural and synthetic substances

Explanation:

natural substances are naturally occurring substances without human interference.

synthetic substances are the man made substances which are made from the natural substances.

Hope it helps..

The number of mmols of HBr are in 17.6 ml of 0.0200 M HBr is 0.352 mmol.

The volume of the solution = 17.6 mL = 0.0176 L

The molarity of the solution = 0.0200 M

The expression for the molarity of the solution is as :

The molarity = moles / volume in L

The number of the moles = molarity × volume

The number of moles = 0.0200 × 0.0176

The number of the moles = 0.000352 mol

The number of the moles in mmoles = 0.352 mmol

Thus, the number of moles of HBr is 0.352 mmoles in the 17.6 ml of the 0.0200 M.

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The gas and liquid hydrogen fluoride (HF) is extremely toxic and corrosive. Its surprising high boiling point is even higher than that of hydrogen iodide despite being the lightest of the hydrogen halides.

In the liquid phase, hydrogen and fluorine atoms form hydrogen bonds as a result of the fluorine atom's strong electronegativity. 1 The van der Waals forces connecting the other hydrogen halides are much weaker.

The molecule HF is commonly called hydrogen fluoride; but its Chemical Abstracts Service name, as found in SciFinder, is hydrofluoric acid. This usage also applies to the other hydrogen halides and has the potential for confusion with the terminology for aqueous solutions of the same compounds.

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Yes, freezing involves the creation of a crystal structure. Freezing is the process of changing a liquid to a solid by cooling it below its freezing point.

During the freezing process, the molecules of the liquid slow down and begin to arrange themselves in a repeating pattern, forming a crystal structure. The crystal structure that forms during freezing is determined by the chemical composition of the substance, its temperature, and the rate at which it is cooled.

If a liquid is cooled slowly, larger and more well-defined crystals will form, whereas if a liquid is cooled quickly, smaller and less well-defined crystals will form. The crystal structure created during freezing can have a significant impact on the physical properties of the solid, such as its strength, transparency, and melting point.

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In the presence of extra Mg3N2, a reaction involving 7 moles of Mg(OH)2 requires 14 moles of water.

A mole is the volume of a substance that contains 6.022 X 1023 of the substance's particles, atoms, ions, molecules, etc. A mole is a unit for counting molecules, ions, or atoms.

The reaction between Mg(OH)2 and H2O has the following balanced chemical equation:

Mg(OH)2 + 2H2O → Mg(OH)2·2H2O

This indicates that 2 moles of water react with 1 mole of Mg(OH)2.

We may determine how many moles of water are required by using the following formula since we have 7 moles of Mg(OH)2.

7 moles Mg(OH)2 × (2 moles H2O / 1 mole Mg(OH)2) = 14 moles H2O.

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The experiment to show that the chemical changes occurring as a log burns in a fireplace are governed by the law of conservation of mass can be performed by weighing the log before and after burning and measuring the amount of ash and gases produced.

The experiment can be carried out by obtaining a dry log of known mass, placing it on a scale, and recording its weight. The log is then burned in a fireplace, and once the fire has been extinguished, the remaining ashes are collected and weighed. Additionally, the volume of gases produced during combustion can be measured using a gas displacement apparatus.

The initial mass of the log should be equal to the final mass of the ash and gases produced, providing evidence for the law of conservation of mass in chemical reactions. The experiment can be repeated with different types of logs to demonstrate that the law of conservation of mass applies to all types of combustion reactions.

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The type of the ClF₃ molecule is the covalent compound. The Chlorine Trifluoride will represents the trigonal bipyramidal geometry.

The Chlorine Trifluoride that is ClF₃ represents the trigonal bipyramidal geometry. In the chlorine trifluoride compound, there are the three bond pairs of the electrons and the two lone pairs of the electrons around the central atom that is the chlorine atom. The total of the five pairs of the electrons represent the trigonal bipyramidal geometry.

The covalent compound is formed by the mutual sharing of the electrons. The chlorine atom will forms the three covalent bonds with the surrounding fluorine atoms in the stable state.

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