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2 years ago

7

Copper, a metal known since ancient times, exists in two stable isotopic forms, 6329Cu (69.09%) and 6529Cu (30.91%). Their atomi

c masses are 62.93 amu and 64.9278 amu respectively. Calculate the average atomic mass of copper.

1 answer:

Svetradugi [14.3K]2 years ago

7 0

Answer:

Wt. Avg. Atomic Weight => 63.35457 amu

Explanation:

Given Isotopic %Abundance fractional Wt Avg

At. Mass (amu) abundance contribution

Cu-63 62.93 69.09 0.6909 43.4783

Cu-65 64.9278 20.0668 0.200668 20.0668

Wt Average of all isotopes = ∑Wt Avg Contributions

= 43.4783 amu + 20.0668 amu = 63.35457 amu

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What is the binding energy of a nucleus that has a mass defect of 5.81*10-^29 kg

IrinaVladis [17]

Answer:

Choice A: Approximately $5.23 \times 10^{-29}$ joules.

Explanation:

Apply the famous mass-energy equivalence equation to find the energy that correspond to the $\rm 5.81\times 10^{-29}$ kilograms of mass.

$E = m \cdot c^{2}$ ,

where

$E$ stands for energy,
$m$ stands for mass, and
$c$ is the speed of light in vacuum.

The speed of light in vacuum is a constant. However, finding the right units for this value can simplify the calculations a lot. What should be the unit of $c$ ?

The mass given is in the appropriate SI unit:

Mass is in kilograms.

Thus, proceed with the speed of light in SI units. The SI unit for speed is meters per second. For the speed of light, $c \approx \rm 3.00\times 10^{8}\;m\cdot s^{-1}$ .

Apply the mass-energy equivalence:

$\begin{aligned} E &= m \cdot c^{2} \\ &= \rm 5.81\times 10^{-29}\; kg \times {\left(3.00\times 10^{8}\; m\cdot s^{-1}\right)}^{2}\\ &\approx \rm 5.23\times 10^{-12}\;kg\cdot m^{2}\cdot s^{-2} \end{aligned}$ .

The unit of energy is not in joules. Don't be alerted. Consider the definition of a joule of energy. One joule is the work done on an object when a force of one newton acts on the object in the direction of the force through the distance of one meter. (English Wikipedia.)

$\rm 1\; J = 1\; N \times 1\; m$ .

However, a force of one newton is defined as the force required to accelerated an object with a mass of one kilogram (not gram) at a rate of one meter per second squared. (English Wikipedia.)

$\begin{aligned}\rm 1\; J &= \rm 1\; N \times 1\; m\\ & = \rm \left(1\; kg\times 1\; m\cdot s^{-2}\right)\times 1\; m\\ &= \rm 1\; kg \cdot m^{2}\cdot s^{-2}\end{aligned}$ .

In other words, the mass defect here is also $\rm 5.23\times 10^{-12}\; J$ .

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3 years ago

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Name the type of bond between atoms in ammonia molecule. Give a reason for your answer

Likurg_2 [28]

Answer:

Covalent bonds are formed when electrons are shared between elements that are nonmetals. The ammonium ion, NH+4 , would have covalent bonds because both nitrogen and hydrogen are nonmetals. ... The rest of the bonds all contain electrons from both hydrogen and nitrogen, so they would be considered ordinary covalent bonds.

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2 years ago

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If is found that 24.68 mL of .1165 M NaOH is needed to titrate .2931 g of an unknown acid to the phenolphthalein end point. Calc

Lemur [1.5K]

Answer: The equivalent mass of the acid is 83.16 grams

Explanation:

To calculate the number of moles for given molarity, we use the equation:

$\text{Moles of solute}={\text{Molarity of the solution}}\times{\text{Volume of solution (in L)}}$

Molarity of $NaOH$ solution = 0.1165 M

Volume of $NaOH$ solution = 24.68 mL = 0.02468 L

Putting values in equation 1, we get:

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( as acidity of NaOH is 1)

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3 years ago

a gas in a container with a fixed volume was originally at a pressure of 317kpa and a temperature of 154k. what is the new press

goldfiish [28.3K]

<h2>Hello!</h2>

The answer is: 4.77atm

<h2>Why?</h2>

Since there's a fixed volume, we can use the the Gay-Lussac's Law which stablish a relation between the pressure and the temperature:

$\frac{P}{T}=k$

<em>P</em> is the volume of the gas

<em>t</em> is the temperature of the gas

<em>k </em>is the proportionality constant

We also have the following equation:

$\frac{P1}{T1}=\frac{P2}{T2}$

Where:

$P2=\frac{P1*T2}{T1}=\frac{317kPa*235K}{154K}=483.73kPa$

We are asked to find the pressure in atm, so we must convert 483.73kPa to atm:

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3 years ago

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D. period is reciprocal of frequency.

Explanation:

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