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3 years ago

Atomic mass is an average of the elements_____.

Chemistry

2 answers:

Dominik [7]3 years ago

8 0

Answer:

The atomic mass of an element is the average mass of the atoms of an element measured in atomic mass unit (amu, also known as daltons, D). The atomic mass is a weighted average of all of the isotopes of that element, in which the mass of each isotope is multiplied by the abundance of that particular isotope.

Explanation:

nexus9112 [7]3 years ago

4 0

Specific chemical element

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Reaction of 0.028 g of magnesium with excess hydrochloric acid generated 31.0 mL of hydrogen gas. The gas was collected by water

MA_775_DIABLO [31]

Explanation:

(a) It is given that magnesium is reacted with hydrochloric acid and the hydrogen evolved is collected at top. This means that hydrochloric acid will be present in a solution (HCl + Water) and the solvent will be water.

Due to evaporation some amount of water will have evaporated and would be present in vapor phase. Therefore, when the reaction occurs only hydrogen will not be present in vapor phase but, will be accompanied by water vapors as well .

Hence, Dalton's law the total pressure of the system will be sum of pressure exerted by hydrogen gas and pressure exerted by water vapors .

Let us assume that the partial pressure of hydrogen gas be " $P_H_{2}$ "

And, the partial pressure of water will be nothing but the vapor pressure of water,

Vapor pressure of water = $P_{water}$

= 19.8 mm Hg

Total pressure of the system = 746 mm Hg

Total pressure = $P_H_{2} + P_{water}$

746 = $P_H_{2}$ + 19.8

or, $P_H_{2}$ = 746-19.8

= 726.2 mm Hg

Hence, partial pressure of hydrogen gas is 726.2 mm Hg.

(b) To calculate volume at STP, we will first calculate at $22^{o}C$ and 726.2 mm Hg and than convert it to STP conditions.

Therefore, to calculate volume at $22^{o}C$ and 726.2 mm Hg we will make use of ideal gas law as follows.

P = 726.2 mm Hg

= $\frac{726.2}{760}$

= 0.955 atm

T = $22^{o}C$

= 22+273.15 = 295.15 K

V = 31 ml = $31 \times 10^{-3}$ Litre

According to the ideal gas law ,

PV = nRT

where, P = pressure of the system ,

V = volume of the gas

N = number of moles

R = 0.0821 liter atm/mole K

T = Temperature

Hence, putting the given values into the above formula as follows.

$0.955 \times 31 \times 10^{-3} = N \times 0.0821 \times 295.15$

N = $1.222 \times 10^{-3}$ moles

Now, the moles of hydrogen won't change. Therefore, let us calculate volume at STP of $1.222 \times 10^{-3}$ moles of hydrogen.

Now, at STP T = 273.15 K , P = 1 atm and N = $1.222 \times 10^{-3}$ moles

$1 \times V = 1.222 \times 10^{-3} \times 0.0821 \times 273.15 K$

V = 0.027398 Litre

= $0.027398 \times 1000$ (as 1 L = 1000 ml)

= 27.398 ml

Therefore, volume of hydrogen at STP is 27.398 ml .

(c) Now, we can write the the reaction for this case as follows.

$Mg + 2HCl \rightarrow MgCl_{2} + H_{2}$

As, weight of magnesium = 0.028 grams

Molar mass of magnesium = 24.3 grams/mole

Number of moles of magnesium = $\frac{mass}{\text{molar mass}}$

= $\frac{0.028}{24.3}$

= $1.15226 \times 10^{-3}$ moles

Since, it can be seen from the reaction that

1 mole of Magnesium = 1 mole of hydrogen

and, moles of hydrogen = $1.15226 \times 10^{-3}$ moles

= 0.001523 moles

Hence, theoretical number of moles of hydrogen that can be produced from 0.028 grams of Mg is 0.001523 moles

8 0

4 years ago

You add 168.90 grams of NaCl to a container and then you add 616.00 grams of water to that same container What is the weight per

erma4kov [3.2K]

Answer:

The weight percent of NaCl in the container is 21.5%

Explanation:

Given that,

Mass of NaCl = 168.90 gram

Mass of water = 616.00 grams

We need to calculate the weight percent of NaCl in the container

Using formula of percentage of weight

$weight\ \%\ of\ component\ of\ the\ solution =\dfrac{weight\ of\ the\ component\ in\ the\ solution}{total\ weight\ of\ the\ solution}\times100$

Put the value into the formula

$weight\ \%\ of\ component\ of\ the\ solution =\dfrac{168.90}{168.90+616.00}\times100$

$weight\ \%\ of\ component\ of\ the\ solution=21.5\%$

Hence, The weight percent of NaCl in the container is 21.5%

5 0

3 years ago

What is the correct electron configuration for copper?

kakasveta [241]

Answer:

[Ar] 3d10 4s1

Explanation:

The correct electronic configuration of copper is [Ar] 3d10 4s1

Copper has atomic number 29 and due to the stability of half filled or fully filled orbitals or shells, the electrons from the 4s jumps to the 3d and makes the 3d shell contain 10 electrons.

This is what I mean:

Cu = Ar 4s2 3d10 is the expected configuration of copper when we follow the principle of filling the various orbitals that is the s, p, d, f orbitals.

But because we write 3d before writing 4s, we have Ar 3d10 4s2. Instead of this configuration becoming the correct one, an electron from the 4s orbital jumps to the 3d orbital to complete the orbital giving the electrons in the 3d orbital 10.

So therefore the correct configuration is Ar 3d10 4s1

4 0

3 years ago

45.1g + 1.786g = (calculator display) & (final answer)

dsp73

The answer is 46.886

8 0

4 years ago

Wht is the boiling point of plastic

Schach [20]

Of the six commonly recycled plastics, four can withstand temperatures of 100 degrees Celsius (212 degrees Fahrenheit) or above. According to Machinist Materials, polyethylene terephthalate -- PET, or recyclable 1 -- has a melting point of 255 degrees Celsius (491 degrees Fahrenheit).

6 0

3 years ago

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