Question 3 of 10
Which event indicates an endothermic chemical reaction?
A. Decrease in temperature
B. Release of heat
C. Increase in thermal energy
D. Production of light



Plz help

Answer:

2

Explanation:

Hope it can help you lovelots

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Answer:

All zeros between other significant digits are significant. The number of significant figures is determined by starting with the leftmost non-zero digit. The leftmost non-zero digit is sometimes called the most significant digit or the most significant figure. For example, in the number 0.004205, the '4' is the most significant figure.

Explanation:

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Answer:

D: Kinetic Energy​

Explanation:

Temperature is a measure of kinetic energy. Temperature is a measure of the average kinetic energy of the particles in an object. When temperature increases, the motion of these particles also increases.

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Answer:

Stoichiometric Calculation:

3 NO₂(g) + H₂O (l) → 2 HNO₃(g) + NO(g)

2 moles of HNO₃ is produced from 3 moles of NO₂.

Therefore, By unitary method:

2.30 moles of HNO₃ produced from the moles of NO₂ = [tex] \dfrac{3}{2} \times 2.30 = \bf{3.45 mol}[/tex]

The number of moles of NO₂ that would be required to produce 2.30 moles of HNO₃ in the presence of excess water in the chemical reaction is 3.45 moles

The balance equation is as follows:

3NO₂(g) + H₂O (l) → 2HNO₃(g) + NO(g)

Water molecules is in excess. Therefore, the limiting reagent is Dinitrogen oxide.

The limiting reagent will determine the amount of product produced.

Therefore,

2 moles of HNO₃ needs 3 moles of NO₂

2.30 moles of HNO₃ will need ? moles of NO₂

cross multiply

number of moles of NO₂  = 2.30 × 3 / 2

number of moles of NO₂  = 6.9 / 2

number of moles of NO₂  = 3.45 moles

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Answer:

reaction is NaHCO3 + HCL = H2CO3 + NaCl

the ratios are 1:1  

the 8 moles of HCl are in excess

so if you use 4 moles of NaHCO3 then you will obtain 4 moles of carbonic acid

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Explanation:

The mass of KCl that exists in 20.3 g of solution containing 1.14% by mass of KCl is 0.23 g

From the question given above, the following data were obtained:

Mass of solution = 20.3 g

Percentage of KCl = 1.14% = 1.14 / 100 = 0.0114

[tex]Percentage = \frac{mass of solute}{mass of solution} * 100\\\\0.0114 = \frac{mass of KCl}{20.3} \\\\[/tex]

Cross multiply

Mass of KCl = 0.0114 × 20.3

Therefore, the mass of KCl in the solution is 0.23 g

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There are two modes in which unstable nuclei of radioactive elements may decay. They are by α - emission or by β - emission. Among the given options, the α - emission is ₆₄¹⁴⁸Gd → ₆₂¹⁴⁴Sm + ₂⁴He. The correct option is D.

According to the theory of radioactive disintegration, the atoms of all the radioactive elements undergo spontaneous disintegration with the emission of α or β particles to yield atoms of new elements. When a radionuclide decays by emitting an  α - particle, it is called α - decay.

When a radionuclide undergoes  α - emission, i.e. a helium nucleus there occurs a decrease of 2 units in the atomic number and a decrease of 4 units in the mass number. The new nuclide produced has an atomic number 2 units less and a mass number 4 units less than the parent.

₆₄¹⁴⁸Gd → ₆₂¹⁴⁴Sm + ₂⁴He represents α - emission.

Thus the correct option is D.

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Answer:

if the cell grows beyond a certain limit, not enough material  will be able to cross the membrane fast enough to sustain the increased cellular volume

Answer: In most cells, this passage of all materials in and out of the cell must occur through the plasma membrane



Explanation:

Explanation:

Leopards have 32 teeth, 4 of which are long, pointed canine teeth. Canine teeth are used to kill prey. Other teeth are for cutting flesh and grinding bone

Answer:

HBr

Explanation:

HBr (Hydrogen Bromide) is a polar molecule because of the unequal electronegativities of Hydrogen and Bromine atoms. Bromine has a higher electronegativity than hydrogen due to which electron bonded pair gets attracted slightly more towards bromine atom making HBr a polar molecule and resulting in a net dipole moment.

Answer:

it may lead to read false measurements

while in an experiment.

that's what I think.

In the first case, the molarity of oxygen gas is 0.0012 mol/L. In the second case, the molarity of oxygen gas is 0.0052 mol/L .

We have to obtain the number of moles of oxygen as follows;

P = 1.00 atm

V = 28.31 mL or 0.02831 L

n = ?

R = 0.082 atm LK-1mol-1

T = 25 °C + 273 = 298 K

n = PV/RT

n=  1.00 atm × 0.02831 L/ 0.082 atm LK-1mol-1 ×  298 K

n = 0.0012 moles

Molarity = Number of moles/Volume = 0.0012 moles/1.00 L =  0.0012 mol/L

For the second case;

P = 4.47 atm

V = 28.31 mL or 0.02831 L

n = ?

R =  0.082 atm LK-1mol-1

T = 25 °C + 273 = 298 K

n = PV/RT

n = 4.47 atm ×  0.02831 L/0.082 atm LK-1mol-1 × 298 K

n = 0.1265/24.436

n = 0.0052 moles

Molarity of oxygen = 0.0052 moles/1.00 L = 0.0052 mol/L

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Answer:

Use the Rydberg Equation 1/λ = R(1/n²(final) - 1/n²(initial) where R = 109,678 cm⁻¹. Substitute initial orbital number and final orbital number and solve for wavelength (λ).

Explanation:

Example:

Assume an electron transition from n = 5 to n = 2.

1/λ = 109,678cm⁻¹(1/2² - 1/5²) = 109,678(0.25 - 0.04)cm⁻¹ = 23,032cm⁻¹

λ = 1/23,032cm⁻¹ = 4.34 x 10⁻⁵cm x 10⁻²m/cm x 10⁹nm/m = 434nm

Answer:

it doesn't house the sweat and oil glands

Explanation:

the epidermis doesn't house the oil and sweat glands but the dermis does

Explanation:

The difference between heat and thermal energy is that thermal energy is not in the process of being transferred; it is not in transit, but remains as part of the internal energy of the system; heat, on the other hand, is energy in transit, i.e. energy in the process of being transferred from a hotter system.

Answer:

see explanation

Explanation:

An AX₂E₂ geometry is derived from an AX₄ parent geometry and is based upon 4 regions of electron density about the central element and defines a tetrahedral geometry and the geometry is bent angular.

An example is the water molecule (H₂O) with two covalent O - H bonds and two free pair electrons on the central oxygen element.

Answer:

3

Explanation:

measurement is the process of finding the value of any Unknown physical quantities in standard value.

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Measurement has been defined as the concept widely used in math and science to quantify an object. It is used to denote the quantification of the event or the object with respect to other or individually.

Hence, the definition of measurement is the process of determining the size or smallness of a physical amount by comparing it to a reference quantity of the same kind as the object.

It has been used to determine the quantity to be small or large based on some predetermined standard or values. It compares the physical quantity like mass can be estimated using kilograms or grams.

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Answer:

The law of conservation of mass states that matter cannot be created or destroyed in a chemical reaction.

For example, when wood burns, the mass of the soot, ashes, and gases equals the original mass of the charcoal and the oxygen when it first reacted. So the mass of the product equals the mass of the reactant.

Another example, solar panels don't create solar energy. They harness energy from the sun and transform it into another type of energy (electricity).

Answer:

they physical quantities that are uneffected by changes to a vector space basis

The water would stand at a height of 1033.6 cm

If the mass of the mercury, m equals the mass of the water, m' at its height,h', then the weight of the mercury W equals the weight of the water, W'

So, W = W'

mg = m'g

ρV = ρ'V' where ρ = density of mercury = 13.60 g/cm³, V = volume of mercury = Ah where A = cross-sectional area of tube = 1.00 cm and h = height of mercury = 76.0 cm, ρ' = density of water = 1.00 g/cm³, V = volume of water = Ah' where A = cross-sectional area of tube = 1.00 cm and h' = height of water.

So, ρV = ρ'V'

ρAh = ρ'Ah'

h' = ρAh/ρ'A

h' = ρh/ρ'

Substituting the values of the variables into the equation, we have

h' = ρh/ρ'

h' = 13.60 g/cm³ × 76.0 cm/1.00 g/cm³

h' = 13.60 × 76.0 cm

h' = 1033.6 cm

So, the water would stand at a height of 1033.6 cm

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Answer:

i k ow its not the exact anwser but ih ope this helps

Explanation:

Energy plays a key role in chemical processes. According to the modern view of chemical reactions, bonds between atoms in the reactants must be broken, and the atoms or pieces of molecules are reassembled into products by forming new bonds. Energy is absorbed to break bonds, and energy is evolved as bonds are made. In some reactions the energy required to break bonds is larger than the energy evolved on making new bonds, and the net result is the absorption of energy. Such a reaction is said to be endothermic if the energy is in the form of heat. The opposite of endothermic is exothermic; in an exothermic reaction, energy as heat is evolved. The more general terms exoergic (energy evolved) and endoergic (energy required) are used when forms of energy other than heat are involved.

A great many common reactions are exothermic. The formation of compounds from the constituent elements is almost always exothermic. Formation of water from molecular hydrogen and oxygen and the formation of a metal oxide such as calcium oxide (CaO) from calcium metal and oxygen gas are examples. Among widely recognizable exothermic reactions is the combustion of fuels (such as the reaction of methane with oxygen mentioned previously).

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The Correct choice is~ B

The elements shown in green boxes are ~ Metalloids

Answer:

Specific heat of ethyl chloride in gas and liquid phases, enthalpy of vaporization and specific heat of solid surface.

Explanation:

In order to determine the final temperature, the heat lost by the chloride needs to be found. This would require the specific heat in both phases and the enthalpy of vaporization. (you will use q=mc(delta)T and q=m(delta)H)

Then the energy gained by the surface needs to be found. This will require the specific heat in order to use the q=mc(delta)T equation.

The enthalpies that we consider to calculate the final temperature of the surface are Specific heat of surface and ethyl chloride as well as Heat of vaporization of liquid & vapor ethyl chloride.

Enthalpy of any reaction tells about the total amount of heat absrobed and released during a chemical reaction.

According to the question, heat released by the surface is absorbed by the ethyl chloride and by absorbing this energy ethyl chlorode will change into the vapor form. In the whole process if we want ot calculate the final temperature on the surface then we should consider:

Hence, required enthalpies are Specific heat of surface and ethyl chloride as well as Heat of vaporization of liquid & vapor ethyl chloride.

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Answer:

The meaning of this principle is building-up.

Explanation:

The Aufbau principle asserts that electrons occupy lower-energy atomic orbitals before filling higher-energy ones (Aufbau is German for "building-up") (Aufbau is German for "building-up"). By using this method, we may forecast the electron configurations for atoms or ions.

The student then places objects of different weights in the beakers, surface tension is the characteristic is the student most likely testing.

Surface tension is the propensity for liquid surfaces that are at rest to condense into the smallest surface area. Razor blades and insects, which have a density greater than that of water, can float on the surface of the water without even becoming partially buried because of surface tension.

A liquid surface's ability to operate like a stretched elastic membrane is known as surface tension. Small liquid drops and soap bubbles have almost spherical shapes, which are indicators of these phenomena. Some insects can stand on the surface of water due to this characteristic.

Surface tension is a crucial factor in many industrial processes, such as detergent formulation, paint optimization, improved oil recovery, medicinal compound performance, and food product stability.

Thus, option C is correct.

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Answer:

Chemical reaction:

2 moles of NO₂ is produced from O₂ moles = 1

Therefore, 2 moles of NO₂ is produced from O₂ moles = [tex]\dfrac{1}{2} \times 13 = \bf{6.5 mol}[/tex]

For 80 % yield no. of moles of O₂ = 6.5 mol

Then for 100% yield no. of moles of O₂ =[tex] \dfrac{6.5}{80\%} =\dfrac{6.5}{\frac{80}{100}} =\dfrac{6.5}{80} \times 100 = \dfrac{650}{80} = \bf 8.125\;mol [/tex]