what is the wavelength of a photon emitted when an electron jumps from n=2 to n= 1 energy level of a single ionized helium atom ?​

This question is describing an spectrophotometry experiment in which the concentration of copper(II) ions has to be determined when 2.50 g of a copper-rich penny is reacted with 50.0 mL of nitric acid. In addition, the absorbance of a sample of the solution turned out to be 0.12 at 635 nm, so that the concentration was estimated as 12.8 g/L.

First of all, we must recall the Beer's law that can be written as follows:

[tex]A=ebC[/tex]

Whereas A is the absorbance of the sample, e the molar absorptivity, b the cuvette's path and C the concentration. However, this problem is not providing sufficient information to calculate the required concentration, however, similar absorbance experiments have graphed (absorbance vs concentration) calibration curves exhibiting trendlines as the one shown below:

[tex]y=0.009647x-0.003655[/tex]

Thus, since y stands for the absorbance and x for the concentration but in g/L not M (mol/L) for those experiments, we can set y equal to 0.12 so we solve for x as the concentration of the copper(II) ions in the sample:

[tex]y=0.009647x-0.003655\\\\x=\frac{0.12+0.003655}{0.009647}\\\\x=12.8g/L[/tex]

Nevertheless, it would be great if you come up with your own trendline, having clear the units for the absorbance vs concentration graph and thus double check your results because the data was not enough for the time being.

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Answer:

1) B. determining what data to collect

2) C. Heat samples of water and ethanol in two separate beakers using a Bunsen burner. Measure the temperatures at which the samples boil using a thermometer. Conduct several trials and record the average temperatures as the boiling points.

3) B. Heat energy overcomes the forces of attraction between the molecules of the substance, so the molecules can move more freely.

4). The addition of thermal energy causes the motion of water molecules to overcome electrostatic forces.

Explanation:

I think these are the answers, i'll confirm when I finish the test.

In an experiment it is known what quantity has to measured, thus the measurement of melting point has been determining what data to collect. Thus, Option B is correct.

To investigate the boiling point of water and ethanol, the samples has to boiled at constant parameters and the data has been collected with several trials. Thus, option C is correct.

Melting has been described as the change of the solid to the liquid state. With melting, there has been heat energy higher than the force of attraction allowing the molecules to move freely. Thus, option B is correct.

The boiling has been the change in the water at liquid state to the gaseous state. With boiling there is thermal energy capable of increasing the motion of water molecules overcoming electrostatic force.

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According to the forces of attraction freezing point and boiling point of water are different and are not related to  strength of electrostatic forces.

Forces of attraction is a force by which atoms in a molecule  combine. it is basically an attractive force in nature.  It can act between an ion  and an atom as well.It varies for different  states  of matter that is solids, liquids and gases.

The forces of attraction are maximum in solids as  the molecules present in solid are tightly held while it is minimum in gases  as the molecules are far apart . The forces of attraction in liquids is intermediate of solids and gases.

The physical properties such as melting point, boiling point, density  are all dependent on forces of attraction which exists in the substances.

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Answer:

Abraham thought that GOD would raise Issac back from the dead. It was a test and they would sacrifice the donkey instead.

The number of moles of the solute in the solution is the product of its volume and molarity. The number of moles of copper sulphate in 0.500 L of 2.30 M solution is 1.15 moles.

Molarity of a solution is the common term used to represent the concentration of a solution. It is the ratio of its number of moles of solute to the volume of solution in liters.

Molarity = no.of moles/volume in L.

Molarity is a temperature dependant quantity.

The given solution has a volume of 0.500 L.

molarity of copper sulphate solution = 2.30 M

Thus, number of moles of copper sulphate solute dissolved in 0.50 L of water is calculated by multiplying the volume with molarity.

No. of. moles of copper sulphate = molarity × volume

= 0.500 L × 2.30 M = 1.15 moles.

Therefore, there will be 1.15 moles of copper sulphate in the solution.

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Answer:

cardiac muscle

Explanation:

because they help the heart to pump blood to all parts of the body

Answer:

Muscle is also very important to everyone because we need our muscles to survive. The HEART is the strongest muscle in our body and is always looking to get stronger. Muscles enable us to be active and exercise. Our strength comes for our muscles and how much they are used.

Explanation:

Answer:

8.7 million species

Explanation:

Scientists have estimated that there are around 8.7 million species of plants and animals in existence.

Heat flows from our body to iron

Answer:

A

Explanation:

A liquid will will have the same color, it will not have the same shape and its volume will always be constant because you are not creating mass.

Hope this helps!

Answer:

An unbalanced force causes the object to change position.

Explanation:

An unbalanced force causes the object on which it is acting to accelerate, changing its position, speed, or direction due to equal forces on opposite sides.

Answer:

2.00n2g

Explanation:

hope its attachments

This question is recalling the behavior of real gases in contrast to ideal gases, defined by the van der Waals equation and the ideal gas law respectively, and a reason behind the increasing discrepancy is required.

In such a way, we can start by considering the attached picture in which the choices are shown and clearly, the answer is "as the polarity of the molecules increase".

The aforementioned can be explained with the concept of intermolecular forces, because ideal gas theory states that ideal gas molecules do not interact one to another, and, as the polarity of the molecules increase, these intermolecular forces increase their frequency and strength, and will lead to the formation of associations, which fail to be numerically modelled by simple equations of state such as van der Waals, Redlich-Kwong, Peng-Robinson, etc,.

These associations are, of course, thoroughly neglected by the ideal gas law whereas the ones included in the van der Waals equation, which are not the most reliable, merely attempt to approach this phenomenon, which cause the mentioned discrepancy. As an additional data, robust equations of state, such as CPA (cubic plus association) are able to provide reliable results when working with highly polar gases but turn out really tough to work with due to its mathematical complexity.

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Answer:

The basic unit of the nervous system is a nerve cell or neuron. The nervous system transmits signals between the brain and the rest of the body, this way, the nervous system's activity controls the ability to move, breathe, see, and think.

Explanation:

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Answer: false

Explanation:

f this helps typically an element wont have a 2 next to it, to see if something is an element or compound check for the element on the periodic table and see if the structure or name matches the one given to you on the question. for example here it is Co2 on the periodic table it's simply written as Co

co2 or carbon dioxide is a  compound not an element, you can even check this on the periodic table

Answer:

true

Explanation:

co2 is carbon dioxide

Hope this helps.

Answer:

0.16 L

Explanation:

Step 1: Write the balanced equation

C₃H₈(g) + 5 O₂(g) → 3 CO₂(g) + 4 H₂O(g)

Step 2: Calculate the moles of CO₂ produced from 0.012 moles of O₂

The molar ratio of O₂ to CO₂ is 5:3. The moles of CO₂ produced are 3/5 × 0.012 mol = 0.0072 mol.

Step 3: Calculate the volume occupied by 0.0072 moles of CO₂ at standard temperature and pressure

At STP, 1 mole of CO₂ occupies 22.4 L.

0.0072 mol × 22.4 L/1 mol = 0.16 L

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Answer:

Individual organisms live together in an ecosystem and depend on one another. ... Some organisms can make their own food, and other organisms have to get their food by eating other organisms. An organism that must obtain their nutrients by eating (consuming) other organisms is called a consumer, or a heterotroph.

Explanation:

1 mL = 0.815 g

11.2 mL = X

X = 11.2 × 0.815

= 9.128 g

mole = 9.128/58

= 0.157 mole

1 mole = 6.02 × 10^23 atoms

0.157 mol = x

X = 0.157/1 × 6.02 × 10^23

= 9.451 × 10^22 atoms of C

please to recheck answers to ensure they are correct

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Answer:

When molecular hydrogen (H2) and oxygen (O2) are combined and allowed to react together, energy is released and the molecules of hydrogen and oxygen can combine to form either water or hydrogen peroxide . These two processes are represented by the two chemical equations shown at right.

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Answer:

The answer is C

Explanation:

Just took the test

Hydrogen bonding is the intermolecular interaction that occurs due to electronegativity differences. Substance B has stronger bonds and requires more energy. Thus, option B is correct.

Hydrogen bonding is present in the water molecules that is because of the electronegativity differences and the dipole-dipole interaction. The hydrogen of the water molecule is bonded to the oxygen molecule.

The hydrogen bonding affects the boiling and the melting point of the substances as more energy are required to change the phase of the matter. So when substance B requires 100ºC than substance A (78.4ºC) it shows strong hydrogen bonding.

Therefore, option B. substance B has a strong hydrogen bond is correct.

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Answer:

Arginine is the most basic among them because it contains guanidine side group, −(CH2)4NHC(=NH)NH2, which is basic. Lysine has two amine groups, which makes it overall basic because of the second isolated amine group (−(CH2)4NH2). Histidine, on the other hand, contains imidazole group, which is also basic.

Explanation:

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Answer:

C. 4%

Explanation:

The answer is 4%

Answer:

About 7.0 × 10³ J or 7.0 kJ

Explanation:

We want to determine the amount of energy needed to raise the temperature of 67 grams of water from 20°C to 45°C.

We can use the heat equation:

[tex]\displaystyle q = mC\Delta T[/tex]

Where C is the specific heat of water.

Substitute and evaluate:

[tex]\displaystyle \begin{aligned} q & = (67\text{ g})\left(\frac{4.2\text{ J}}{\text{g-$^\circ$C}}\right)\left(45^\circ \text{ C}- 20.^\circ\text{ C}\right) \\ \\ & = (67\text{ g})\left(\frac{4.2\text{ J}}{\text{g-$^\circ$C}}\right)(25^\circ \text{ C}) \\ \\ & = 7.0\times 10^3 \text{ J}\end{aligned}[/tex]

Recall that there are 1000 J in a kJ. Hence:

[tex]\displaystyle \begin{aligned} q & = 7.0\times 10^3 \text{ J} \cdot \frac{1\text{ kJ}}{1000\text{ J}} \\ \\ & = 7.0 \text{ kJ}\end{aligned}[/tex]

In conclusion, it will take about 7.0 × 10³ J or 7.0 kJ of energy to raise the temperature of 67 grams of water from 20 °C to 45 °C.

Answer:

There are 27 Valence electrons : )

4+1+1+1+6+4+1+1+4+1+1+1 is 27

Explanation:

There are a total of [5×1]+[2×4]+[7]=21[5×1]+[2 × 4 ] + [ 7]=21 valence electrons

Answer:

Chlorine Iodine is a compound made out of one Chlorine molecule and one Iodine molecule

Explanation:

Answer:

Ionic bond occurs between two atoms that have different:

a) Electron

Explanation:

according to the definition of ionic bond,

it is the electrostatic force of attraction that holds the two oppositely charged ions together and an ionic bond or electrovalent bond is formed when one atom gains electrons while the other atom loses electrons from its outermost level or orbit.

This question is describing two chemical equations whereby the concentration of ammonia has to be determined. The first reaction is between 25.00 mL of ammonia and 50.00 mL of 0.100-M HCl whose excess was neutralized with 21.50 mL of 0.050-M Na₂CO₃ and thus, the concentration ammonia in the cloudy solution was determined as 0.114 M.

First of all we need to go over the titration of the excess HCl with Na₂CO₃ by writing the chemical equation it takes place when they react:

[tex]2HCl+Na_2CO_3\rightarrow 2NaCl+CO_2+H_2O[/tex]

Whereas the mole ratio of HCl to Na₂CO₃ is 2:1 and the volume of the HCl leftover is determined as follows:

[tex]V_{HCl}^{leftover}=\frac{2*0.050M*21.50mL}{0.100M} =21.5mL[/tex]

Next, we infer that the consumed volume of HCl by the ammonia solution was:

[tex]V_{HCl}^{consumed}=50.00mL-21.50mL=28.5 mL[/tex]

Then, we write the chemical equation that takes place between ammonia and HCl:

[tex]HCl+NH_3\rightarrow NH_4Cl[/tex]

Whereas the mole ratio is now 1:1, which means that the concentration of ammonia was:

[tex]M_{NH_3}=\frac{28.5mL*0.100M}{25.00mL}\\\\ M_{NH_3}=0.114M[/tex]

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Answer:

397 L

Explanation:

Recall the ideal gas law:

[tex]\displaystyle PV = nRT[/tex]

If temperature and pressure stays constant, we can rearrange all constant variables onto one side of the equation:

[tex]\displaystyle \frac{P}{RT} = \frac{n}{V}[/tex]

The left-hand side is simply some constant. Hence, we can write that:

[tex]\displaystyle \frac{n_1}{V_1} = \frac{n_2}{V_2}[/tex]

Substitute in known values:

[tex]\displaystyle \frac{(3.31 \text{ mol})}{(100 \text{ L})} = \frac{(13.15\text{ mol })}{V_2}[/tex]

Solving for V₂ yields:

[tex]\displaystyle V_2 = \frac{(100 \text{ L})(13.15)}{3.31} = 397 \text{ L}[/tex]

In conclusion, 13.15 moles of argon will occupy 397* L under the same temperature and pressure.

(Assuming 100 L has three significant figures.)