Which statement about Niels Bohr's atomic model is true?
O Higher orbits have lower energies.
O Each orbit has a specific energy level.
O Electrons can exist in any energy level.
O Orbits close to the nucleus have no energy.

Answer: a. C₂H₂

              b. 43.2 g

              c. 1.4 moles

Explanation: In a chemical reaction, when a reagent is completely consumed and limits the product formed is called Limiting Reagent. The reactant that is left is the Excess Reactant.

For the burning of acetylene:

[tex]2C_{2}H_{2}+5O_{2} \rightarrow 4CO_{2}+2H_{2}O[/tex]

a. An easy way to determine which reactant is limiting, is to divide the number of moles of each reactant by the coefficient in the balanced reaction. The component that gives the smallest number is the limiting reagent.

The ratio for acetylene is

[tex]\frac{2.4}{2}[/tex] = 1.2

For oxygen:

[tex]\frac{7.4}{5}=[/tex] 1.48

So, the limiting reactant is acetylene.

b. From the balanced reaction, for each 2 moles of acetylene is consumed, 2 moles of water is produced. Then, for 2.4 moles, it will be produced 2.4 moles of water.

Mol is mass in grams divided by molar mass of the component.

[tex]n=\frac{m}{M}[/tex]

Molar mass of water is M = 18 g/mol.

Then, mass of water produced:

m = n.M

m = 2.4(18)

m = 43.2 g

With 2.4 moles of acetylene, it will be produced 43.2 grams of water.

c. For each 2 moles of acetylene consumed, 5 moles of oxygen is also consumed. So, for 2.4 moles:

2 moles = 5 moles

2.4 moles = n

[tex]n=\frac{2.4*5}{2}[/tex]

n = 6 moles

For 2.4 moles of acetylene, it is consumed 6 moles of oxygen. Then, the excess is

7.4 - 6 = 1.4

The excess reactant remaining is 1.4 moles of oxygen.

Answer:

1000 kJ.mmole / 1000 J.mole

Explanation:

To solve this, we need to analyze the given data.

We have a number which is 87.1 J/mmole.C (I'm assuming it has the J at the beggining because if not, then you are missing some data) and the final result is kJ/mol.C

The only unit that has not changed in the process was the °C, while the mole and J change respectively. In this case, we need to know the conversion factor of mmole to mole and J to kJ.

In the case of a mole:

1 mole --------> 1000 mmole

In the case of Joule:

1 kJ ----------> 1000 J

So the first thing we will do is to change from J to kJ:

87.1 J * 1 kJ / 1000 J = 0.0871 kJ

Now let's convert mmol to mole:

0.0871 kJ/mmole.C * 1000 mmole / 1 mole = 87.1 kJ/mole.C

As you can see, there's is practicly no change at all with the units, so putting all together it would be:

Hope this helps

Answer:

The kinetic molecular theory of matter states that: Matter is made up of particles that are constantly moving. All particles have energy, but the energy varies depending on the temperature the sample of matter is in. This in turn determines whether the substance exists in the solid, liquid, or gaseous state.

Explanation:

Answer:

True

Explanation:

A drug is "a medicine or other substance which has a physiological effect when ingested or otherwise introduced into the body"(Oxford dictionary).

In the body, there are numerous macromolecules that perform various functions. These macromolecules often function as the target molecules to which different drugs may be bound.

A drug functions by binding strongly to a macromolecule with which it interacts in order to produce the desired biological action.

Answer:

c = 0.528 J/g.°C

Explanation:

Given data:

Mass of titanium = 43.56 g

Heat absorbed = 0.476 KJ  = 476 j

Initial temperature = 20.5°C

Final temperature = 41.2°C

Specific heat capacity = ?

Solution:

Specific heat capacity:

It is the amount of heat required to raise the temperature of one gram of substance by one degree.

Formula:

Q = m.c. ΔT

Q = amount of heat absorbed or released

m = mass of given substance

c = specific heat capacity of substance

ΔT = change in temperature

ΔT = 41.2°C - 20.5°C

ΔT = 20.7 °C

476 J = 43.56 g × c × 20.7 °C

476 J = 901.692 g.°C × c

c = 476 J / 901.692 g.°C

c = 0.528 J/g.°C  

Answer:

308 moles of sodium

Explanation:

The balanced equation for the chemical reaction between sodium metal (Na) and water (H₂O) is the following:

2 Na(s) + 2 H₂O → 2 NaOH(aq) + H₂(g)

From the equation, we can see that 2 moles of Na react with 2 moles of H₂O to give 2 moles of NaOH and 1 mol of H₂ (hydrogen gas). So the stoichiometric mole ratio between Na and H₂ is: 2 mol Na/1 mol H₂. Thus, we multiply the mole ratio by the moles of H₂ to be produced to obtain the moles of Na required:

moles of Na required =  2 mol Na/1 mol H₂ x 154 moles H₂ = 308 moles Na

Therefore, 308 moles of sodium are needed to produce 154 moles of hydrogen gas.

Answer:

3.51× 10²³ formula units

Explanation:

Given data:

Mass of CaO = 32.7 g

Number of formula units = ?

Solution:

First of all we will calculate the number of moles.

Number of moles = mass/molar mass

Number of moles = 32.7 g/ 56.1 g/mol

Number of moles = 0.583 mol

Number of formula units:

1 mole = 6.022 × 10²³ formula units

0.583 mol ×  6.022 × 10²³ formula units / 1 mol

3.51× 10²³ formula units

The number 6.022 × 10²³ is called Avogadro number.

Answer: Sol:-

Data provided in the question is :-

Atomic mass of isotope -1 = 64 amu

Atomic mass of isotope -2 = 66 amu

Atomic mass of isotope -3 = 67 amu

Atomic mass of isotope -4 = 68 amu

Atomic mass of isotope - 5 = 70 amu

Percentage abundace of isotope - 1 = 48.89 %

Percentage abundance of isotope -2 = 27.81 %

Percentage abundance of isotope - 3 = 4.11%

Percentage abundance of isotope-4 = 18.57%

Percentage abundance of isotope - 5 = 0.62 %

Formula used :-

Average atomic mass of an element =[ {(atomic mass of isotope-1 * percentage abundance of isotope-1) + ( atomic mass of isotope-2 * percentage abundance of isotope -2) + ( atomic mass of isotope -3 * percantege abundance of isotope-3 ) + ( atomic mass of isotope-4 * percentage abundance of isotope-4) + (atomic mass of isotope-5 * percentage abundance of isotope-5)} / 100]

Calculation :-

Put all the value in the formula :-

Average atomic mass of an element = [{(64 * 48.89) + (66 * 27.81) + (67 * 4.11) + (68 * 18.57) + (70 * 0.62)} / 100] amu

= [{(3128.96) + (1835.46) +(257.37) + (1262.76) + (43.4)} / 100] amu

= {(6528.04) / 100} amu

= 65.2804 amu

Average atomic mass of an element is = 65.2804 amu

Then this mass is approximatly equal to atomic mass of zinc so this element would be zinc

atomic mass of zinc = 65.38 \approx 65.2804 amu

Answer:

Explanation:

-We convert Ca(OH)₂ grams to moles using its molar mass:

-We convert K₂SO₃ moles to grams using its molar mass:

-One formula unit of HCl is HCl. We convert molecules to moles using Avogadro's number:

-At STP, one mol of any gas occupies 22.4 L:

Answer:

Via covalent bonds

Explanation:

Atoms in molecules are bonded together via covalent bonds. Covalent bonds are bonds that are formed by sharing of the valence electrons between two atoms.

The atoms can be of the same kind or of different kinds.

Answer:

the change in energy when one substance dissolves in another

Explanation:

The enthalpy changes are the heat changes accompanying physical and chemical changes. Actually, an enthalpy change is the difference between the sum of the heat contents of products (final state) and sum of the heat contents of reactants (initial state).

There are basically two types of heat changes that accompanies are reaction which are:

Therefore, the change in energy when one substance dissolves in another defines the enthalpy of solution.

Enthalpy of solution is the heat liberated or absorbed when one mole of a substance (solute) is dissolved in a specified volume of solvent (water).

Answer:

3.3 moles of H₂O.

Explanation:

We'll begin by writing the balanced equation for the reaction. This is illustrated below:

4NH₃ + 5O₂ —> 6H₂O + 4NO

From the balanced equation above,

4 moles of NH₃ reacted to produce 6 moles of H₂O.

Finally, we shall determine the number of mole of H₂O produced by the reaction of 2.2 moles of NH₃. This can be obtained as follow :

From the balanced equation above,

4 moles of NH₃ reacted to produce 6 moles of H₂O.

Therefore, 2.2 moles of NH₃ will react to produce = (2.2 × 6)/4 = 3.3 moles of H₂O.

Thus, 3.3 moles of H₂O were obtained from the reaction.

Answer:sulfur

Explanation:

Answer: The equipment best suited for extinguishing each type of fire are listed below:

--> Fire extinguisher: Large fire on the floor

--> Overturned beaker: Small benchtop fire

--> Fire blanket: clothing fire.

Explanation:

Fire outbreaks is a common event that can be prevented in a standard chemistry laboratory with the aid of fire safety equipments.

The method used by these equipments to extinguish fire is to suffocate the fire by obstructing the source of oxygen, by reducing the heat with the use of water and removing the fuel or oxygen source.

These fire safety equipments should be highly visible and easily accessible in a laboratory. Example of fire safety equipments includes:

--> Fire extinguisher: A laboratory personnel needs to be trained in the use of this since it's made up of different types. it can be used to extinguish ( put out) large fire on the floor.

--> Overturned beaker: this can be used to suffocate small fire on the bench which is also common in the laboratory.

-->Fire blanket: This should be used in the event that a person’s body or clothing catches fire.

Answer: inside

Explanation:

Answer:

direct and indirect contact

Explanation:

if you touch a doorknob right after an infected person than you make be exposed to the disease.

The temperature and the strength of the metallic link are the two most crucial variables that can impact how malleable a metal or alloy is.

A metal is a substance that has a shiny look when freshly processed, polished, or shattered, and conducts electricity and heat rather effectively. Generally speaking, metals are malleable and ductile.

The amount of pressure that a metal can sustain without breaking can be used to gauge its malleability. Varied metals have different degrees of malleability because of variations in their crystal structures.

The temperature of the metal and the strength of the metallic connection are the two parameters that define how malleable a metal or metal alloy will be.

Thus,  The kind of the metallic connection can have a significant impact on how easily metal atoms can rearrange themselves.

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Answer:

That Jupiter's gravitational force is much stronger than Earth's gravitational force.

Answer:

7.23m/s²

Explanation:

Given parameters:

Initial velocity  = 0m/s

Final velocity  = 60m/s

Time taken  = 8.3s

Unknown:

Acceleration of the dragsters = ?

Solution:

Acceleration is defined as the rate of change of velocity with time taken.

So;

    Acceleration  = [tex]\frac{Final velocity - Initial velocity }{time}[/tex]  

Acceleration  = [tex]\frac{60 - 0}{8.3 }[/tex]    = 7.23m/s²

Answer:

arsenic don't mind does it have to be longer

The statement, that describes the elements is not a metal is "arsenic.

Metals are shiny, opaque elements that transfer heat and electricity well. They are malleable and easily lose electrons to produce positive ions (cations).

Arsenic is the third element in the periodic table's fifteenth column. It is a metalloid or semi-metal because it possesses chemical and physical properties that are transitional between a metal and a non-metal.

Hence the correct option is A.

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Answer:

Wave

Explanation:

Wave refers to any disturbance that carries energy from one place to another.

Wave refers to disturbance or variation that occur in a body travelling or in motion which travels from one medium to another by transmitting energy from one location which is the origin to another location without transporting matter.

Therefore, Wave refers to any disturbance that carries energy from one place to another

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Answer:

dwarf planets lack the gravitational forces needed to pull in and accumulate all of the material found in their orbits

Explanation:

Answer:

Explanation:

When performing a multiplication or division calculation, significant figures in the calculated result are dictated by the significant figures of the measured numbers. The calculated result should have the same significant figure as the measured number in the calculation with the fewest significant figures.

According to the rule guiding significant figures during mathematical operations; when performing multiplications or divisions involving multiple numbers, the final answer should have the same significant figures as the number with the least significant figures.

For example: if 10.54 and 101.25 are multiplied, the final answer should have the same significant figure as 10.54 because this is the number with the least significant figure among the numbers involved in the entire operation.

10.54 has 4 significant figures while 101.25 has 5 significant figures. The final answer should, therefore, have 4 significant figures.

Thus; 10.54 x 101.25 = 1,067

Answer:

B. materials change their properties.

Explanation:

In a chemical change, materials often change their properties because a re-arrangement of atoms takes place.

A chemical change is one in which new kind of matter is formed.

It is always accompanied by energy changes.

Answer:

there are three equivalent bonding MOs of equal energy and one unique bonding MO.

Explanation:

Let us recall that according to the principles of the molecular orbital theory, when a compound is formed, the number of bonding molecular orbitals must be equal to the number of antibonding molecular orbitals.

Now methane is formed from one carbon atom and four hydrogen atoms. There are four bonding molecular orbitals and four antibonding molecular orbitals.

Three out of the four bonding molecular orbitals are degenerate while one is unique.

Answer:

a) 24.7 mol

b) 790 g

Explanation:

Step 1: Given data

Step 2: Convert "T" to Kelvin

We will use the following expression.

K = °C + 273.15

K = 23°C + 273.15 = 296 K

Step 3: Calculate the moles (n) of oxygen

We will use the ideal gas equation.

P × V = n × R × T

n = P × V/R × T

n = 3.00 atm × 200. L/(0.0821 atm.L/mol.K) × 296 K = 24.7 mol

Step 4: Calculate the mass (m) corresponding to 24.7 moles of oxygen

The molar mass (M) of oxygen ga sis 32.00 g/mol. We will calculate the mass of oxygen using the following expression.

m = n × M

m = 24.7 mol × 32.00 g/mol = 790 g

Answer:

Q = 2640.96 J

Explanation:

Given data:

Mass of He gas = 10.7 g

Initial temperature = 22.1°C

Final temperature = 39.4°C

Heat absorbed = ?

Solution:

Specific heat capacity:

It is the amount of heat required to raise the temperature of one gram of substance by one degree. Specific heat capacity of He is 14.267 J/g.°C

Formula:

Q = m.c. ΔT

Q = amount of heat absorbed or released

m = mass of given substance

c = specific heat capacity of substance

ΔT = change in temperature

ΔT = 39.4°C - 22.1°C

ΔT = 17.3°C

Q = 10.7 g× 14.267 J/g.°C ×  17.3°C

Q = 2640.96 J