Explain the statement "atomic weight or molecular weight is a relative weight"

Suppose a group of volunteers is planning to build a park near a local lake. The lake is known to contain low levels of arsenic

Kisachek [45]

Answer:

A) 10.75 is the concentration of arsenic in the sample in parts per billion .

B) 7,633.66 kg the total mass of arsenic in the lake that the company have to remove.

C) It will take 1.37 years to remove all of the arsenic from the lake.

Explanation:

A) Mass of arsenic in lake water sample = 164.5 ng

The ppb is the amount of solute (in micrograms) present in kilogram of a solvent. It is also known as parts-per million.

To calculate the ppm of oxygen in sea water, we use the equation:

$\text{ppb}=\frac{\text{Mass of solute}}{\text{Mass of solution}}\times 10^9$

Both the masses are in grams.

We are given:

Mass of arsenic = 164.5 ng = $164.5\times 10^{-9} g$

$1 ng=10^{-9} g$

Volume of the sample = V = $15.3 cm^3$

Density of the lake water sample ,d= $1.00 g/cm^3$

Mass of sample = M = $d\times V=1.0 g/cm^3\times 15.3 cm^3=15.3 g$

$ppb=\frac{164.5\times 10^{-9} g}{15.3 g}\times 10^9=10.75$

10.75 is the concentration of arsenic in the sample in parts per billion.

B)

Mass of arsenic in $1 cm^3$ of lake water = $\frac{164.5\times 10^{-9} g}{15.3}=1.075\times 10^{-8} g$

Mass of arsenic in $0.710 km^3$ lake water be m.

$1 km^3=10^{15} cm^3$

Mass of arsenic in $0.710\times 10^{15} cm^3$ lake water :

$m=0.710\times 10^{15}\times 1.075\times 10^{-8} g=7,633,660.130 g$

1 g = 0.001 kg

7,633,660.130 g = 7,633,660.130 × 0.001 kg=7,633.660130 kg ≈ 7,633.66 kg

7,633.66 kg the total mass of arsenic in the lake that the company have to remove.

C)

Company claims that it takes 2.74 days to remove 41.90 kilogram of arsenic from lake water.

Days required to remove 1 kilogram of arsenic from the lake water :

$\frac{2.74}{41.90} days$

Then days required to remove 7,633.66 kg of arsenic from the lake water :

$=7,633.66\times \frac{2.74}{41.90} days=499.19 days$

1 year = 365 days

499.19 days = $\frac{499.19}{365} years = 1.367 years\approx 1.37 years$

It will take 1.37 years to remove all of the arsenic from the lake.

3 0

2 years ago

Calculate the enthalpy of combustion, δh∘comb, for c6h14. you'll first need to determine the balanced chemical equation for the

Vedmedyk [2.9K]

<span>Answer: Enthalpy Change = (6 x -393.5) + (7 x -285.8) - (-204.6) + (19/2) 0.....??? like.. (6 x Enth CO2) + ( 7 x Enth H2O) - (Enth C6H14) + (19/2) Enth O2</span>

3 0

2 years ago

_________is a process in which o2 is released as a by-product of oxidation-reduction reactions

Kisachek [45]

Answer : The combustion is a process in which oxygen is released as a by-product of oxidation-reduction reactions.

Explanation :

Combustion reaction : It is defined as the reactions in which a hydrocarbon reacts with oxygen gas to produce carbon dioxide and water.

The chemical equation of combustion reaction is:

$CH_4+2O_2\rightarrow CO_2+2H_2O$

The combustion reaction is also a redox reaction.

Redox reaction or Oxidation-reduction reaction : It is defined as the reaction in which the oxidation and reduction reaction takes place simultaneously.

Oxidation reaction : It is defined as the reaction in which a substance looses its electrons. In this, oxidation state of an element increases. Or we can say that in oxidation, the loss of electrons takes place.

Reduction reaction : It is defined as the reaction in which a substance gains electrons. In this, oxidation state of an element decreases. Or we can say that in reduction, the gain of electrons takes place.

The combustion reaction is also a redox reaction in which the carbon shows oxidation by the addition of oxygen or removal of hydrogen and oxygen shows reduction by the addition of hydrogen or removal of oxygen.

Hence, the combustion is a process in which oxygen is released as a by-product of oxidation-reduction reactions.

6 0

2 years ago

Select the correct set of quantum numbers (n, l, ml, ms) for the first electron removed in the formation of a cation for stronti

matrenka [14]

Answer:

5,0,0,-1/2

Explanation:

The quantum numbers are a way to characterize the electrons, and so, identify the region that it's more probable to find it (orbital). They are:

- Principal quantum number (n): represents the shell or level, and varies from 1 to 7, and are represented by the letter K, L, M, N, O, P, and Q.

- Azimuthal quantum number (l): represents the subshell or sublevel, and is represented by 0,1,2,3.., and for the letters s, p, d, f,...

- Magnetic quantum number (ml): represents the orbital. It varies from -l to +l passing by 0. Each orbital can have 2 electrons.

- Spin quantum number (ms): represents the spin of the electron. It can be +1/2 or -1/2.

The strontium has an atomic number equal to 38, by the Linus Pauling's diagram, the electronic distribution is:

1s²2s²2p⁶3s²3p⁶4s²3d¹⁰4p⁶5s²

The valence electron is at the subshell 5s, which has only one magnetic quantum number: 0. Because it has 2 electrons, the first one has spin =1/2, and the other -1/2. So the first electron of the formation of cation has quantum numbers:

n = 5; l = 0; ml = 0; ms = -1/2

7 0

2 years ago

Acetaldehyde shows two UV bands, one with a lmax of 289 nm ( 5 12) and one with a lmax of 182 nm ( 5 10,000). Which is the n p*

UkoKoshka [18]

Answer:

The bands are due to:

λmax = 289 nm n→π* transition (E = 12)

λmax = 182 nm π→π* transition (E=10000)

Explanation:

The two types of acetaldehyde transition are as follows:

n→π* and π→π*

From the attached diagram we have to:

ΔEn→π* < ΔEπ→π*

ΔEα(1/λ)

Thus:

λn→π* > λπ→π*

In n→π* spin forbidden, the intensity is low. Thus, the molar extinction E for n→π* is very low.

The same way, for π→π* spin allowed the intensity is high. Thus, the molar extinction coefficient E for π→π* is high too.

The bands are due to:

λmax = 289 nm n→π* transition (E = 12)

λmax = 182 nm π→π* transition (E=10000)

5 0

2 years ago