How is a pure substance different from a mixture?


A. Pure substances cannot be separated by physical means.
B. Mixtures cannot be separated by physical means.
C. A pure substance is heterogeneous.
D. A mixture is made of one substance.

Each enzyme has an optimum pH level at which it shows its highest activity. Below or above this pH, the activity level probably decreases.

Enzymes are biological catalysts in living bodies. There are thousands of individual enzymes present in human body itself. Each enzymes are having their specific functions.

Enzymes have a pocket like receptor structure on which the substrate can attach. Hence enzymes provide a perfect platform for a chemical reaction. Each enzymes has an optimum pH and temperature at which it can shows it highest activity.

For example, the enzyme pepsin functions in digestion in humans works at a pH of 2. Similarly the enzyme amylase will be active only at pH around 7. This way, enzymes activity is significantly dependent on the pH.

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The atomic mass of the atom with 104 protons and 157 neutrons has been 261 amu.

An atom has been consisted of the positively charged nucleus and the negatively charged electrons revolving around the nucleus. The nucleus has been consisted of neutrons and protons.

The transfer of electrons between the atoms impart charge to the atom and helps in the reactivity of the atom. The atomic mass in an atom has been the mass of the nucleus. It has been a constant quantity in an atom.

Since the atomic mass has been the mass of the nucleus:

Atomic mass = Neutrons + Protons

Atomic mass = 157 + 104

Atomic mass = 261 amu

The atomic mass of the atom with 104 protons and 157 neutrons has been 261 amu.

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Answer:If the calorimeter decreases in temperature over the course of the reaction:

[tex]Q_{rxn}=Positive[/tex]

[tex]Q_{cal}=Negative[/tex](heat is lost by the caloriemter)

Explanation:

Whenever reaction takes place in calorimeter tone out of two things can a happen:

1. If the temperature of calorimeter increases: During a reaction when heat is released in the calorimter. This heat released is then absorbed by the calorimeter (Law of Conservation of Energy) which results in increase in temperature of calorimeter.

Those reaction which add on heat to their surrounding are termed as Exothermic reaction.

[tex]Q_{rxn}=Negative[/tex]

[tex]Q_{cal}=Positive[/tex] (Heat gained by the calorimeter)

2. If the temperature of calorimeter decreases: During a reaction when heat is lost from the calorimter. This heat loss is due to the absorption of heat by reactants during the reaction (Law of Conservation of Energy) which results in decrease in temperature of calorimeter.

Those reaction which absorbs heat from their surrounding are termed as Endothermic reaction.

[tex]Q_{rxn}=Positive[/tex]

[tex]Q_{cal}=Negative[/tex](heat is lost by the caloriemter)

Final answer:

The major functional groups for biomolecules include hydroxyl, methyl, carbonyl, carboxyl, amino, phosphate, and sulfhydryl. Examples of compounds where these functional groups are found include carbohydrates, amino acids, and organic acids.

Explanation:

The major functional groups for biomolecules include hydroxyl, methyl, carbonyl, carboxyl, amino, phosphate, and sulfhydryl. These functional groups confer specific chemical properties to molecules bearing them.

For example, hydroxyl groups (-OH) are found in carbohydrates, alcohols, and many other organic compounds. Amino groups (-NH2) are found in amino acids, the building blocks of proteins. Carboxyl groups (-COOH) are found in organic acids, such as fatty acids.

Carbohydrates are formed by dehydration synthesis, a process in which monomers bind together by combining their functional groups and generating water molecules as byproducts.

The atomic number of sulfur is 16. The electron configuration for an electronically neutral atom of sulfur is 1 s 22 s 22 p 63 s 23 p 5. The correct option is d.

The electronic configuration of an atom is the position of the electrons present inside the atoms. This process identified the position of electrons inside the atoms.

The different shells have different energy levels, and these energy levels are also reflected in the energy of electrons.

So, as the atomic number of sulfur is 16. If its electronic configuration is done. There will be 1 electron is the s orbital, 22 in s2 and 22 in the p orbital. The last orbital has 5 electrons.

Therefore, the electron configuration for an electronically neutral atom of sulfur is 1 s 22 s 22 p 63 s 23 p 5. The correct option is d.

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A Hydrogen atom only contains a single electron (1 e). Therefore for this atom, the quantum number which determines the energy of an electron is best represented only by the principal quantum number. The principal quantum number has a symbol of n.

Answer:

n

The correct answer would be freezing point. The other three would not be the answer because fammability, ph, and toxicity are all examples of chemical properties.

Answer:

C - Variable

Explanation:

Let’s see all the options in detail.

Apparatus: These are the equipment’s used in the experiment. Irrespective of the experiment result, the apparatus remains unchanged from start till the end.

Constant: These are factors that are fixed and does not change throughout the experiment.

Variable: A variable is any factor in an experiment that changes. As per dictionary, variable literally means something that varies i.e. change.  

Hypothesis: This is the underlying explanation in response to which the experiment is being conducted. Also, in an experiment, the hypothesis is not considered a factor at all.

Therefore, the correct answer is C.

The electron configuration of copper cation:

₂₉Cu²⁺ 1s² 2s² 2p⁶ 3s² 3p⁶ 3d⁹ or [Ar] 3d⁹.

The electron configuration of copper cation:

₄₇Ag⁺ 1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p⁶ 4d¹⁰ or [Kr] 4d¹⁰.

Copper and silver lose their outer s-orbital electrons before they lose their outer d-orbital electrons.

Each electron configuration is consistent with the color, copper solution is blue, silver solution is colorless.

The electron configuration of Cu²⁺ is 1s² 2s² 2p⁶ 3s² 3p⁶ 3d⁹. The electron configuration of Ag⁺ is 1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p⁶ 4d¹⁰.

The observed color of Cu²⁺ is typically blue, while the observed color of Ag⁺ is colorless. The electron configurations of these cations are consistent with their observed colors.

Electronic configuration refers to the arrangement of electrons in an atom, ion, or molecule. It describes the distribution of electrons among different energy levels, orbitals, and subshells within an atom or ion.

The electronic configuration is represented using a notation that indicates the energy levels (principle quantum numbers), subshells (s, p, d, f), and the number of electrons in each subshell. The Aufbau principle, Pauli exclusion principle, and Hund's rule are used to determine the order of filling the orbitals and the spin states of the electrons.

Cu²⁺ has an incomplete d-orbital with 9 electrons, which gives rise to a blue color due to the absorption of light in the visible spectrum. The absorption of light corresponds to the promotion of an electron from a lower energy d-orbital to a higher energy level.

On the other hand, Ag⁺ has a fully filled d-orbital with 10 electrons, which does not result in the absorption of visible light. As a result, Ag⁺ appears colorless.

The observed colors of Cu²⁺ and Ag⁺ ions are a result of the electronic configuration and the interaction of light with the d-electrons in the transition metals.

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Answer:

Physical property is density.

Explanation:

This check needs precision. Gold is a dense metal, 19.32 grams per cubic centimeter. For that you have to calculate the density, weighing the piece on a scale, then you would fill a test tube with water and introduce the piece and note how much the water has risen. Density is defined as the mass divided by the displaced volume. If the result you get is close to 19 it will be a 24-karat gold piece.

The volume of the object is 23.06 cm³

We have an object of given mass and density.

We have to calculate the volume of this object.

The following relation exists between mass and density -

m = d x v

d - density of body

m - mass of body

v - volume of body

According to the question -

m = d x v

Rewrite the relation as follows -

v = m/d

Substitute the values -

v = 455.6 / 19.3 = 23.06 cm³.

Hence, the volume of the object is 23.06 cm³.

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To prepare 250 mL of a 0.235 M solution of KCL, you would need roughly 4.38 grams of solid KCl. This is calculated using the formula for molarity, converting volume in ml to liters, and then using the molar mass of KCl to convert moles to grams.

The task is to find out how many grams of solid KCl are needed to prepare 250 mL of 0.235 M solution. This is a question about molarity, which is a measure of the concentration of a solute in a solution.

Start by knowing that molarity (M) is defined as moles of solute per liter of solution. Hence, we can calculate the moles of KCl needed using the formula: moles = Molarity * Volume (in liters). In this case, the volume in litres is 250 mL / 1000 = 0.250 L.

Moles of KCl = Molarity * Volume

Moles of KCl = 0.235 M * 0.250 L = 0.05875 mol

Now to convert moles to grams, we use the molar mass of KCl, which is approximately 74.55 g/mol.

Mass of KCl = Moles * Molar mass

Mass of KCl = 0.05875 mol * 74.55 g/mol = approximately 4.38 g

So, you would need around 4.38 grams of solid KCl to prepare 250 mL of a 0.235 M solution.

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To prepare 250 mL of a 0.235 M solution of KCl, you need a. 4.38 grams of KCl.

To prepare 250 mL of a 0.235 M solution of KCl, you need 4.38 grams of KCl.

The formula to find moles is:

Given:

First, calculate the moles of KCl:

Next, convert the moles of KCl to grams using the molar mass of KCl.

Calculate the grams of KCl:

Therefore, to prepare 250 mL of a 0.235 M solution of KCl, you need 4.38 grams of KCl.

Correct question is: How many grams of solid kcl are needed to prepare 250 ml of 0.235 m solution?

a. 4.38 g

b. 5.67 g

c. 3.67 g

d. 2.78 g

Answer: Option (D) is the correct answer.

Explanation:

Water table is defined as the upper most level of water that is present under the ground surface where there is permanent separation of soil or rocks with water.

Water table is maintained through a natural process as when it rains then the rain water seeps through the ground and reaches below the ground.

Water table is also known as ground water table.

Therefore, we can conclude that the water table is the upper surface of underground water.

Density of the given sample is 10.50 g /cm³ which is the density of silver.

Density  of a substance is it's mass per unit volume.It is denoted by capital letter 'D'.It has SI unit of kg/m³.For a pure substance, density has numerical value which is same as it's mass.

Different materials have different densities  which is  found to be relevant to substance's purity and packaging.Osmium and Iridium are densest known elements.

Density is an intensive property because there is a narrow range of densities across the samples. It does not change with respect to the initial mass .It shows how much mass of substance is present in given amount of volume.

For the mentioned data, density is calculated as,mass/volume

which is 25/2.38=10.504 g/cm³

10.504 g/cm³ is the density of silver and hence the sample is of silver.

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