Chlorofluorocarbons (cfcs) are greenhouse gases that, for a specific amount of mass, trap significantly more heat than CO2. how can you classify cfcs?

The sensitivity of the test is 33.3%,

the specificity of the test is 90%,

the positive predictive value of the test is 75%, and

the negative predictive value of the test is 60%.

Given that 11.3% of the U.S. population aged 65 and over has Alzheimer's disease, we are to evaluate a proposed screening test for Alzheimer's disease with the following results:

Test Results Positive Negative Alzheimer's Disease 150300No Alzheimer's Disease50 450

a. Estimating the sensitivity of the test

Sensitivity of the test refers to the proportion of people who are genuinely positive for a disease and have tested positive.

In other words, the proportion of people with Alzheimer's who correctly test positive.

Sensitivity is calculated as follows:

Sensitivity = (Number of true positives) / (Number of true positives + Number of false negatives)

Number of true positives = 150 (as given in the table)

Number of false negatives = 300 (as given in the table)

Sensitivity = (150) / (150 + 300)

                 = 0.333 or 33.3%

b. Estimating the specificity of the test

The specificity of the test refers to the proportion of individuals who do not have the disease and test negative for it.

In other words, the proportion of people without Alzheimer's who correctly test negative.

Specificity is calculated as follows:

Specificity = (Number of true negatives) / (Number of true negatives + Number of false positives)

Number of true negatives = 450 (as given in the table)

Number of false positives = 50 (as given in the table)

Specificity = (450) / (450 + 50)

                 = 0.900 or 90%

c. Computing the positive predictive value of the test

Positive predictive value refers to the proportion of individuals who test positive for a disease and have the disease.

In other words, the probability of having the disease given that the test is positive.

Positive predictive value is calculated as follows:

Positive predictive value = (Number of true positives) / (Number of true positives + Number of false positives)

Number of true positives = 150 (as given in the table)

Number of false positives = 50 (as given in the table)

Positive predictive value = (150) / (150 + 50)

                                         = 0.75 or 75%

d. Computing the negative predictive value of the test

Negative predictive value refers to the proportion of individuals who test negative for a disease and do not have the disease.

In other words, the probability of not having the disease given that the test is negative.

Negative predictive value is calculated as follows:

Negative predictive value = (Number of true negatives) / (Number of true negatives + Number of false negatives)

Number of true negatives = 450 (as given in the table)

Number of false negatives = 300 (as given in the table)

Negative predictive value = (450) / (450 + 300) = 0.600 or 60%

Thus, the sensitivity of the test is 33.3%, the specificity of the test is 90%, the positive predictive value of the test is 75%, and the negative predictive value of the test is 60%.

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Answer:

The natural phenomenon used to describe the length of a meter is the speed of light. The length of a meter is the length a light path travels in 1/(299792458) seconds through a vacuum.

The definition is better due to the uncertainty involved in the use of the length of a standard meter stick because the length of the meter stick could change due to atmospheric conditions from place to place

Explanation:

Answer:

In a physical change the appearance or form of the matter changes but the kind of matter in the substance does not. However in a chemical change, the kind of matter changes and at least one new substance with new properties is formed.

Because only certain size electron orbits are allowable, the frequency and energy of the electron is quantized

According to the Bohr model of the atom, an electron moves from a lower to a higher energy level when it absorbs energy. This energy is released when the electron returns to ground state.

According to the Bohr model, only certain size electron orbits are allowable hence the frequency and energy of the electron is quantized.

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Answer:

1.10 g/mL

Explanation:

The amount of volume an object displaces is the amount of volume that object takes up.

7.87 - 1.67 = 6.2

The object has a volume of 6.2 mL.

You have the mass (6.82 g) and the volume (6.2 mL).  Divide the two value to find the density.

(6.82 g)/(6.2 mL) = 1.10 g/mL

The density of the object is 1.10 g/mL.

Answer:

Question says , the height of the student = 4 feet, ... This means, if the student goes for swimming in the pool, however he does not know swimming, he will not be drowned until he is suffering from an injury or external force.

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Answer to Question #96220 in Molecular Physics | Thermodynamics for Kaleesh

Answers>Physics>Molecular Physics | Thermodynamics

Question #96220

a) Determine the enthalpy changes, ΔH for the reaction below, given the following reactions and subsequent ΔH values. Please rewrite the amended chemical reaction equation again.

N2H4 (l) + CH4O (l) CH2O (g) + N2 (g) + 3H2 (g)

2NH3 (g) N2H4 (l) + H2 (g) ΔH = 22.5kJ

2NH3 (g) N2 (g) + 3H2 (g) ΔH = 57.5 kJ

CH2O (g) + H2 (g) CH4O (l) ΔH = 81.2 kJ

b) Given that the enthalpy of vaporization for water as below:

H2O (l) H2O (g) ΔH vap = 44.0 kJ mol-1

Calculate enthalpy ΔH for each of the following processes:

i) Evaporating 3.00 moles of water

ii) Evaporating 3.00 grams of water

i) Condensing 20.0 grams of water

(3 Marks)

c) Use the enthalpy of formation data to calculate the enthalpy of the reaction below.

2C2H6 (g) + 7O2 6H2O (g) + 4CO2 (g)

Answer: The percent error for the student's work is 12.3%

Explanation: To calculate the percent error, we need to first determine the difference between the accepted value of the density of calcium (1.54 g/cm³) and the value measured by the student (1.35 g/cm³). This difference is 1.54 - 1.35 = 0.19 g/cm³.

To express this difference as a percentage, we can divide it by the accepted value and multiply by 100%:

Percent Error = (Difference / Accepted Value) * 100%

= (0.19 / 1.54) * 100%

= 12.3%

Therefore, the percent error for the student's work is 12.3%. This means that their measured value is off by about 12.3% from the accepted value.

The reaction that is occurring in this question is:

H2 + I2 -> 2 HI

As we can see, the molar ratio for H2 and I2 is 1:1, one mole of H2 for each mole of I2, and the molar ratio between any reactant and HI is 1:2, which means the number of moles of product will be two times more than the number of moles of the reactants

We have:

3.0 moles of H2

2.0 moles of I2

1.0 moles of HI

According to the molar ratio, we should have the name number of moles of I2 and H2, which means that H2 is in excess and I2 is the limiting reactant with 2 moles

If we have 2 moles of I2, and the molar ratio of I2 and HI is 1:2, we should have 4 moles of HI being produced

Therefore the theoretical number of moles is 4.0 moles of HI from 2.0 moles of I2

A soap film is thin enough to exhibit interference of light, meaning that the light waves passing through it can reinforce or cancel each other out.

When the thickness of the soap film decreases to a molecular scale, the film acts as a thin-film interferometer and the reflection across the entire visible spectrum becomes zero.

Because the light waves passing through the front and back surfaces of the film interfere destructively, leading to zero reflection. This condition is known as the "minimum reflection" and is used to accurately measure the thickness of thin films.

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Answer:

Radio waves

Explanation:

Radio waves, on the other hand, have the lowest energies, longest wavelengths, and lowest frequencies of any type of EM radiation. In order from highest to lowest energy, the sections of the EM spectrum are named: gamma rays, X-rays, ultraviolet radiation, visible light, infrared radiation, and radio waves.

Answer:

Tungsten(VI) fluoride, also known as tungsten hexafluoride, is an inorganic compound with the formula WF6. It is a toxic, corrosive, colorless gas, with a density of about 13 g/L (roughly 11 times heavier than air.[

Explanation:

The WF6 molecule is octahedral with the symmetry point group of Oh. The W–F bond distances are 183.2 pm. Between 2.3 and 17 °C, tungsten hexafluoride condenses into a pale yellow liquid having a density of 3.44 g/cm^3 at 15 °C. At 2.3 °C it freezes into a white solid having a cubic crystalline structure, the lattice constant of 628 pm, and a calculated density of 3.99 g/cm^3. At −9 °C this structure transforms into an orthorhombic solid with the lattice constants of a = 960.3 pm, b = 871.3 pm, and c = 504.4 pm, and the density of 4.56 g/cm3. In this phase, the W–F distance is 181 pm, and the mean closest intermolecular contacts are 312 pm. Whereas WF6 gas is one of the densest gases, with the density exceeding that of the heaviest elemental gas radon (9.73 g/L), the density of WF6 in the liquid and solid-state is rather moderate. The vapor pressure of WF6 between −70 and 17 °C can be described by the equation

log10 P = 4.55569 −

1021.208

T + 208.45,

where the P = vapor pressure (bar), T = temperature (°C).

A redox reaction is a chemical reaction in which one or more of the reacting species undergoes oxidation and one or more undergoes reduction. An oxidizing agent is an element or compound that oxidizes another substance, while a reducing agent is an element or compound that reduces another substance.

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Answer: You would write elements in period 1, 2, 3, and period 4 but you would stop at chromium

Explanation: It would have been too long for me to write every symbol

The new boiling point of the solution is 80.09oC.

The molar mass of an unknown solute can be calculated from the data provided. When an unknown solute is dissolved in a solvent, it affects the freezing point and boiling point of the solution. The amount of depression is directly proportional to the amount of solute present in the solution. The equation that relates these quantities is given by:ΔTf = Kf .m i. ΔTf = depression in freezing point (Freezing point of solvent - freezing point of solution)Kf

= molal freezing point depression constant (specific for each solvent)m i

= molality of the solution (mol of solute / kg of solvent)Here, the depression in freezing point is given as

ΔTf = 2.4oC.

The molality of the solution is given by;mi = 0.056 kg / 78.11 gmol-1

= 0.000718 mol/kgUsing the values of Kf and ΔTf for benzene from literature

(Kf = 5.12 K kg mol-1,

ΔTf = 5.5oC), we can calculate the molar mass of the unknown solute:

5.5oC = 5.12 K kg mol-1 × 0.000718 mol/kg × wSolving for w,

w = 0.117mol/kgMolar mass,

M = mass / moles

= 0.056 kg / 0.117 mol

= 0.478 kg/mol or 478 gmol-1Now, the elevation in boiling point can also be calculated using the equation:

ΔTb = Kb .m i.ΔTb

= elevation in boiling pointKb

= molal boiling point elevation constant (specific for each solvent)mi

= molality of the solution (mol of solute / kg of solvent)For benzene,

Kb = 2.53 K kg mol-1, and

mi = 0.000718 mol/kg

ΔTb = Kb .

m i = 2.53 K kg mol-1 × 0.000718 mol/kg

= 0.00182 K Therefore, the new boiling point of the solution will be 80.09oC (normal boiling point of benzene is 78.11oC).The Molar Mass of the unknown solute is 478 gmol-1. The new boiling point of the solution is 80.09oC.

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Answer:

0.35M NaOH and 0.0375M HCl.

Explanation:

NaOH reacts with HCl as follows:

NaOH + HCl → NaCl + H2O

Where 1 mole of NaOH reacts per mole of HCl

To solve the first question we must find the moles of HCl that reacted = Moles NaOH in the unknown. With the moles and the volume we can find its molar concentration:

Moles HCl = Moles NaOH:

0.0350L * (0.25mol / L) = 0.00875 moles NaOH

In 25.0mL = 0.0250L:

0.00875 moles NaOH / 0.0250L =

0.35M NaOH

For the second question, the moles of NaOH = moles HCl. With the 200mL = 0.200L the molarity is:

Moles NaOH = Moles HCl:

0.015L * (0.5mol / L) = 0.0075 moles HCl / 0.200L =

0.0375M HCl

A. Each is found outside the nucleus

The IR spectrum of Acetylferrocene will differ from that of Ferrocene because of the carbonyl stretching and bending modes that appear in the Acetylferrocene.

The IR spectrum of Acetylferrocene will differ from that of Ferrocene due to the carbonyl stretching and bending modes that appear in the Acetylferrocene.

Ferrocene and Acetylferrocene have similar IR spectra since they both have the Fe-Cp stretching and bending modes. The acetyl group of Acetylferrocene is reflected by an intense band in the 1700-1750 cm-1 range, which is due to carbonyl stretching.

                                     In Acetylferrocene, the IR spectra are dominated by the presence of the acetyl group's vibration, resulting in a change in the frequency of stretching vibration from 200 to 220 cm−1. Another change in the IR spectra of Acetylferrocene is the presence of two bands due to C-O stretching at 1230-1260 cm-1 in addition to the appearance of a strong band due to C-H bending vibrations in the 1410-1450 cm-1 region.

                           Ferrocene does not have a carbonyl group, which is why it will not display the carbonyl stretching and bending vibrations in the IR spectra. This is the most significant difference between the two IR spectra. So, we can conclude that the IR spectrum of Acetylferrocene will differ from that of Ferrocene due to the presence of the carbonyl group.

Therefore,  The IR spectrum of Acetylferrocene will differ from that of Ferrocene because of the carbonyl stretching and bending modes that appear in the Acetylferrocene.

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Using methyl ethyl ketone instead of benzophenone in a Grignard lab experiment would yield a secondary alcohol rather than a tertiary alcohol, and the reaction could proceed faster due to increased reactivity.

Using methyl ethyl ketone instead of benzophenone in a Grignard lab experiment would alter the result due to differences in reactivity and the products formed. Here's a step-by-step explanation:
1. Reactivity: Methyl ethyl ketone is less sterically hindered compared to benzophenone, which makes it more reactive towards Grignard reagents. This could potentially result in a faster reaction.
2. Products formed: The Grignard reagent reacts with the carbonyl group in both methyl ethyl ketone and benzophenone. The difference in their structures leads to different products.
- For benzophenone: Grignard reagent attacks the carbonyl group, forms an alkoxide intermediate, and then, upon aqueous workup, produces a tertiary alcohol.
- For methyl ethyl ketone: Grignard reagent attacks the carbonyl group, forms an alkoxide intermediate, and then, upon aqueous workup, produces a secondary alcohol.
So, using methyl ethyl ketone instead of benzophenone in a Grignard lab experiment would yield a secondary alcohol rather than a tertiary alcohol, and the reaction could proceed faster due to increased reactivity.

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Taking into account the definition of calorimetry, the correct answer is las option: the initial temperature of the copper piece is 364°C.

Calorimetry is the measurement and calculation of the amounts of heat exchanged by a body or a system.

Sensible heat is defined as the amount of heat that a body absorbs or releases without any changes in its physical state (phase change).

So, the equation that allows to calculate heat exchanges is:

Q = c×m×ΔT

where:

In this case, you know:

Replacing in the expression to calculate heat exchanges:

If two isolated bodies or systems exchange energy in the form of heat, the quantity received by one of them is equal to the quantity transferred by the other body. That is, the total energy exchanged remains constant, it is conserved.

Then, the heat that the copper gives up will be equal to the heat that the water receives. Therefore:

- Qcopper = + Qwater

- 0.39 J/gC × 240 g× (42 C - Initial temperature of copper)= 4.18 J/gC× 400 g× (42 C - 24 C)

Solving:

- 93.6 J/C× (42 C - Initial temperature of copper)= 30,096 J

- 93.6 J/C× 42 C- (- 93.6 J/C)× Initial temperature of copper= 30,096 J

- 3,931.2 J +93.6 J/C × Initial temperature of copper= 30,096 J

93.6 J/C × Initial temperature of copper= 30,096 J+ 3,931.2 J

93.6 J/C × Initial temperature of copper= 34,027.2  J

Initial temperature of copper=34,027.2  J÷ 93.6 J/C

Initial temperature of copper= 364 °C

Finally, the initial temperature of the copper is 364 °C.

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Answer:

the correct answer is 364

q = m * c * ΔT

where q is the heat absorbed or released, m is the mass of the substance, c is the specific heat capacity of the substance, and ΔT is the change in temperature.

We can assume that the heat lost by the copper is gained by the water, so:

q(copper) = -q(water)

where the negative sign indicates that the copper loses heat while the water gains heat.

The specific heat capacity of copper is 0.39 J/g °C, so:

q(copper) = 240.0 g * 0.39 J/g °C * (T(copper) - 24.0 °C)

The specific heat capacity of water is 4.18 J/g °C, so:

q(water) = 400.0 g * 4.18 J/g °C * (42.0 °C - T(copper))

Setting q(copper) equal to -q(water), we get:

240.0 g * 0.39 J/g °C * (T(copper) - 24.0 °C) = -400.0 g * 4.18 J/g °C * (T(copper) - 42.0 °C)

Simplifying and solving for T(copper), we get:

T(copper) = [(400.0 g * 4.18 J/g °C * 42.0 °C) + (240.0 g * 0.39 J/g °C * 24.0 °C)] / (240.0 g * 0.39 J/g °C + 400.0 g * 4.18 J/g °C)

T(copper) = 364.1 °C

Therefore, the initial temperature of the copper piece was 364.1 °C.

Hence, the answer is "364 °C".

In 50 grams of water at 90°C, it is expected 35 grams will dissolve considering the solublity is 70g/ 100 grams of water.

Solubility increases when temperature increases, which means more grams of a substance can be disolved if temperature is higher.

The best is through a solubility curve chart as the one below.

As observe in the graph the solubility at 90°C using 100 grams of water is 70g/ 100 grams of water; this implies in 50 grams the solubility is 30 grams.

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Answer:

Elements

Gold, copper

Compounds

Sodium chloride, Sulphur dioxide, Aluminium oxide,

Mixture

Brass, rainwater, distilled water, sugar solution,muddy water

Explanation:

Answer:

28 g/mol

Explanation:

since the atomic weight of Nitrogen is 14 you take the amount of it and multiply it by that so in this case it would be this equation:

14 x 2 = 28

Answer:

2-methylpropanoic acid

Explanation:

no probs chief

Answer:

Al2 O3 or 2:3

Explanation:

The aluminum oxide consists of two elements, which are oxygen atoms and aluminum atoms, and there are 2 aluminum atoms and 3 oxygen atoms in aluminum oxide. The ratio from aluminum atoms to oxygen atoms is 2:3.

There are two types of chemical compound one is covalent compound and other is ionic compound, covalent compound formed by sharing of electron and ionic compound formed by complete transfer of electron. Therefore, the ratio of aluminum atoms to oxygen atoms in aluminum oxide is  2:3.

Chemical Compound is a combination of molecule, Molecule forms by combination of element and element forms by combination of atoms in fixed proportion.

An ionic compound is a metal and nonmetal combined compound.  Ionic compound are very hard. They have high melting and boiling point because of strong ion bond. The ratio of aluminum atoms to oxygen atoms in aluminum oxide is  2:3. Aluminium oxide is an ionic compound.

Therefore, the ratio of aluminum atoms to oxygen atoms in aluminum oxide is  2:3.

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The number of moles of 10 billion oxygen molecules is  1.66 x 10⁻¹⁴ moles.

The number of moles of a substance equals the ratio of its given mass in a chemical reaction to the mass of one mole of that substance.

One mole of any substance equals Avogadro's number, that is, 6.023 × 10²³.

6.023 x 10²³ molecules of oxygen --------> 1 moles of oxygen

1 x 10¹⁰ molecules of oxygen --------------> ?

= (1 x 10¹⁰) / (6.023 x 10²³)

= 1.66 x 10⁻¹⁴ moles

Thus, the number of moles of 10 billion oxygen molecules is  1.66 x 10⁻¹⁴ moles.

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