Elements are described as pure substances because?

A. they have no charge.


B. they are found in nature.


C. they can be produced in a laboratory.


D. they cannot be separated into parts by physical means.

change from solid to liquid

Explanation:

The amount in moles of the excess reactant left is 0.5 mole

2ZnS (s) + 3O₂(g) --> 2ZnO (s) + 2SO₂(g)

From the balanced equation,

2 moles of ZnS reacted with 3 moles of O₂

From the balanced equation,

2 moles of ZnS reacted with 3 moles of O₂

Therefore,

4.2 moles of ZnS will react with =(4.2 × 3) / 2 = 6.3 moles of O₂

From the calculations made above, we can see that only 6.3 moles of O₂ out of 6.8 moles given, is required to react completely with 4.2 moles of ZnS.

Thus, ZnS is the limiting reactant and O₂ is the excess reactant.

The excess reactant is O₂. Thus the mole remaining after the reaction can be obtained as illustrated below:

Mole of O₂ remaining = (Mole of O₂ given) - (Mole of O₂ that reacted)

Mole of O₂ remaining = 6.8 - 6.3

Mole of O₂ remaining = 0.5 mole

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The pKb of the base is 2.

To find the pKb of a base, we can use the relationship between pKb and pH. The pKb is calculated using the following formula:

pKb = 14 - pH

Given that the pH of the 1 M solution of the base is 12, we can substitute this value into the formula to find the pKb:

pKb = 14 - 12

pKb = 2

Therefore, the pKb of this base is 2.

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Answer:

Yes, its carried out under carefully controlled conditions because it might some times have a negative impacts towards humans.

Answer:

32 gm O

Explanation:

there are 16 gm of O in each 18 gm of water ....the other two grams are H

so there would be 32 gm of oxygen in 36 gm water

In addition to the name of the chemical and any special warnings, there are several other important pieces of information that should be included on the label of stock solutions prepared in the lab. These include:

1. Concentration: The concentration of the stock solution should be clearly indicated. This can be expressed as molarity (M), percentage (%), or other appropriate units.

2. Date of Preparation: It is important to include the date when the stock solution was prepared. This helps in tracking the age and shelf life of the solution.

3. Storage Conditions: The recommended storage conditions should be provided, such as temperature, light sensitivity, or any other specific requirements to maintain the stability and integrity of the solution.

4. Hazard Symbols or Codes: If the chemical is hazardous, it is important to include the appropriate hazard symbols or codes, such as GHS (Globally Harmonized System) pictograms, to indicate the potential risks associated with the solution.

5. Safety Precautions: Any necessary safety precautions or handling instructions should be clearly stated, including the use of personal protective equipment (PPE), ventilation requirements, and handling procedures.

6. Batch or Lot Number: If applicable, a batch or lot number can be included to help with traceability and quality control.

It is essential to ensure that all information on the label is accurate, up-to-date, and compliant with local regulations and safety standards. Properly labeled stock solutions help to minimize the risks associated with handling and using chemicals in the laboratory.

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Option (a) is the answer because the reaction is endothermic and therefore ΔHRXN > 0 .

Equilibrium is a state in which the forward and backward reaction rates are the same, and the concentration of the reactants and products does not change over time. The reaction in the question is: HF(aq)+ H2O(l) arrows both ways H3O+ + F-(aq)When the temperature is raised, the conductivity of the solution will rise because, in the presence of heat, HF breaks down to produce more ions. The ionization of HF increases with temperature. If HF is more ionized, the conductivity of the solution will be higher.The reaction is endothermic because heat is absorbed in order to break the H-F bond. The energy of the system increases when the reactants are converted to products as a result of this process, and so ΔHRXN is positive. Option (a) is the answer because the reaction is endothermic and therefore ΔHRXN > 0.

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The purpose of this lab is to determine the specific heat of a metal by measuring the amount of heat it takes to raise its temperature. This lab is an inquiry lab, as it involves measuring how changing one variable (the amount of heat added to the metal) affects another variable (the temperature change of the metal).

The specific heat of a substance is the amount of heat required to raise the temperature of 1 gram of that substance by 1 degree Celsius. The specific heat of a metal is important for a variety of applications, such as cooking and engineering.In this lab, you will use a calorimeter to measure the amount of heat that is transferred to a metal when it is heated. The calorimeter is a device that measures the heat energy that is transferred between two objects.To determine the specific heat of the metal, you will measure the mass of the metal, the initial temperature of the metal, the final temperature of the metal, and the amount of heat that is transferred to the metal.

You will then use these measurements to calculate the specific heat of the metal using the following equation:

specific heat = (heat transferred / mass of metal) * (final temperature of metal - initial temperature of metal)

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Answer:

Grignard reagents are formed by the reaction of magnesium metal with alkyl or alkenyl halides. They're extremely good nucleophiles, reacting with electrophiles such as carbonyl compounds

Explanation:

hope this helps!

Answer: Potassium (K) has the lowest electronegativity among the given elements.

Explanation:

Electronegativity is a measure of an element's ability to attract electrons towards itself when it is involved in a chemical bond with another element. Potassium has the lowest electronegativity because it has only one valence electron that is located far from the nucleus, making it easier to lose that electron and become a positively charged ion. In contrast, nitrogen, lithium, and bromine have higher electronegativities because they have more valence electrons or the valence electrons are closer to the nucleus, making it more difficult to remove or share electrons.

The element with the lowest electronegativity among the given options is potassium (K). Potassium has an electronegativity value of approximately 0.82 on the Pauling scale, which is the lowest value among the four elements listed. In contrast, nitrogen (N) has an electronegativity of approximately 3.04, bromine (Br) has an electronegativity of approximately 2.96, and lithium (Li) has an electronegativity of approximately 0.98. Electronegativity is a measure of an atom's ability to attract electrons towards itself in a chemical bond. The lower the electronegativity value, the less the atom attracts electrons towards itself.

Brainliest?

Answer:

1.38 moles

Explanation:

My teacher gave us the answer on a quiz so here if y’all want a explanation I’ll give y’all one tho

Answer:

Potassium Bromide

Explanation:

not sure but i think thats it

Answer:

12 - x = 20 - 5x

Add 5x on both sides,

12 - x + 5x = 20 - 5x

12 + 4x = 20

Subtract 12 on both sides,

12 - 12 + 4x = 20 - 12

4x = 8

Divide 4 on both sides,

4x / 4 = 8 / 4

x = 2

Hence proved.

Answer:

This would give us Helium 4.

Explanation:

Lithium7 has 3 protons, 4 neutrons and 3 electrons.

Removing  1 Proton 1 electron and 2 neutrons would form an element with

2 protons 2 electrons and 2 neutrons.

This is Helium 4.

Answer:

2A =B + 2C hope that helps

Explanation:

For a series of weak acids, the increase in pKa means that the conjugate bases become more stable.

The term pKa refers to the negative logarithm of the acid dissociation constant. This is a constant that shows the extent to which an acid is dissociated in solution.

As the pKa of a series of  weak acids increases, the conjugate bases become more stable.

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Answer:

The fourth answer choice.

Explanation:

This is the correct answer because dropping it, carrying it, won't to anything to change the physical state of the matter (the bowl).

Hope this helps! :)

The total pressure in the flask is 24.91 atm.

To calculate the total pressure in the flask, we need to convert the partial pressures of each gas to the same units, preferably atm.

Partial pressure of nitrogen = 9.65 atm

Partial pressure of oxygen = 631 torr = 0.831 atm (since 1 atm = 760 torr)

Partial pressure of ammonia = 1467 kPa = 14.43 atm (since 1 atm = 101.3 kPa)

Now, we can find the total pressure by adding up the partial pressures of each gas:

Total pressure = 9.65 atm + 0.831 atm + 14.43 atm = 24.91 atm

Therefore, the total pressure in the flask is 24.91 atm.

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Answer:

Explanation:

This link will take you to a work sheet that I think might help.

Therefore, it takes approximately 23.2 kJ of energy to boil 100 mL of water.

The correct answer is D. 100 mL × 1g divided by 1mL × 1mol divided by 18.02g × 4.186 kJ/mol = 23.2 kJ

To calculate the energy required to boil 100 mL of water, we need to use the specific heat capacity of water, which is approximately 4.186 J/g·°C. The molar mass of water is 18.02 g/mol.

First, we convert the volume of water from milliliters to grams:

100 mL × 1 g/1 mL = 100 g

Then, we calculate the number of moles of water:

100 g × 1 mol/18.02 g = 5.548 mol

Finally, we multiply the number of moles by the molar heat of vaporization of water, which is approximately 40.65 kJ/mol:

5.548 mol × 4.186 kJ/mol = 23.2 kJ

Therefore, it takes approximately 23.2 kJ of energy to boil 100 mL of water.

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Answer:

The National Institute of Standards and Technology defines STP differently as absolute pressure of 1 atm (101.325 kPa, 14.696 psi) and 20 degrees Celsius (293.15 degrees Kelvin, 68 degrees Fahrenheit).

Answer:

hi im baby patrick :)

Explanation:

Answer:

Detail is given below.

Explanation:

Given data;

Abundance of Berkmarium-95 = 70%

Abundance of Berkmarium-97 = 28%

Abundance of Berkmarium-94 = 2%

Average atomic mass closer to which isotope = ?

Solution:

1st of all we will calculate the average atomic mass of Berkmarium.

Average atomic mass = (abundance of 1st isotope × its atomic mass) +(abundance of 2nd isotope × its atomic mass) + (abundance of 3rd isotope × its atomic mass) / 100

Average atomic mass  = (70×95)+(28×97)+(2×94) /100

Average atomic mass =  6650 + 2716+ 188 / 100

Average atomic mass= 9554 / 100

Average atomic mass = 95.54 amu

The average atomic mass is closer to the isotope Berkmarium-95  because it is present in abundance as compared to the other two isotope. So this isotope constitute most of the part of Berkmarium.

Answer:

Explanation:

A petrifying well is a well which gives objects a stone-like appearance. If an object is placed into such a well and left there for a period of months or years, the object acquires a stony exterior.

The molarity when .772 moles are dissolved in .500 Liters of water is 0.0015M. The molarity when .453 moles are dissolved in .450 Liters of water is 0.001M.

The term molarity is defined as the number of moles of solute dissolved in per litre of solution. The unit of molarity is mole, which is denoted by the symbol "M".

M = Number of moles of solute / litre in solution

1. Number of moles of solute = .772 moles

so, 0.772 / 500

= 0.0015 M

2. Number of moles of solute =  .453 moles

so, .453 / 450

= 0.001 M

Thus, The molarity when .772 moles are dissolved in .500 Liters of water is 0.0015M. The molarity when .453 moles are dissolved in .450 Liters of water is 0.001M.

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Answer:

when he collided with the passerby

Explanation:

Cells in many-celled organisms can look the same or different, depending on the type of organism and the function of the cells.

In general,multi-cellular(many-celled) organisms have specialized cells that perform specific functions, such as muscle cells, nerve cells, and blood cells. These cells are different in structure and function, but they all work together to maintain the organism's health and survival.

For example, in humans:

Therefore, cells in many-celled organisms can look the same or different, depending on the function of the cells. While many-celled organisms have specialized cells, some cells have the same structure and function.

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Answer:

The balanced chemical equation for the reaction between BaCl2 and Na2SO4 is:

BaCl2 + Na2SO4 → 2 NaCl + BaSO4

This equation shows that one mole of BaCl2 reacts with one mole of Na2SO4 to produce two moles of NaCl and one mole of BaSO4. Therefore, to determine how many moles of NaCl can be produced from 2.5 moles of BaCl2, we need to use the stoichiometry of the reaction.

Steps:

Step 1: Write down the balanced chemical equation for the reaction between BaCl2 and Na2SO4.

BaCl2 + Na2SO4 → 2 NaCl + BaSO4

Step 2: Identify the stoichiometric ratio of BaCl2 to NaCl from the balanced chemical equation.

From the balanced chemical equation, we see that 1 mole of BaCl2 produces 2 moles of NaCl.

Step 3: Calculate the number of moles of NaCl produced from 2.5 moles of BaCl2.

Using the stoichiometric ratio, we can calculate the number of moles of NaCl produced from 2.5 moles of BaCl2 as follows:

2.5 moles BaCl2 x (2 moles NaCl / 1 mole BaCl2) = 5 moles NaCl

Therefore, 2.5 moles of BaCl2 can produce 5 moles of NaCl.

Answer:

Ver explicacion

Explanation:

Cristalización y disolución de cloruro de sodio: equilibrio físico dinámico

Conversión de oxígeno gaseoso en ozono - equilibrio químico

Condensación y evaporación de un líquido - equilibrio físico dinámico

Reacción entre H2 y 12 para producir Hl - equilibrio químico

Una solución saturada de azúcar - equilibrio físico dinámico

El equilibrio alcanzado en los procesos físicos se llama procesos físicos. El equilibrio físico se llama. Ejemplos de tales procesos físicos incluyen; condensación y evaporación, cristalización y disolución, etc.

Un equilibrio dinámico ocurre en un sistema químico cuando la reacción directa y la reacción inversa se desarrollan a la misma velocidad.