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Lena [83]
4 years ago
15

Enrico Fermi (1901-1954) was a famous physicist who liked to pose what are now known as Fermi problems in which several assumpti

ons are made in order to make a seemingly impossible estimate. Probably the most famous example is the estimate of the number of piano tuners in Chicago using the approximate population of the city and assumptions about how many households have pianos, how often pianos need tuning, and how many hours a given tuner works in a year.Another famous example of a Fermi problem is \"Caeser\'s last breath\" which estimates that you, right now, are breathing some of the molecules exhaled by Julius Caesar just before he died.
Assumptions:1. The gas molecules from Caesar\'s last breath are now evenly dispersed in the atmosphere.
2. The atmosphere is 50 km thick, has an average temperature of 15 �C, and an average pressure of 0.20 atm.
3. The radius of the Earth is about 6400 km.
4. The volume of a single human breath is roughly 500 mL.
1) Perform the following calculations, reporting all answers to two significant figures. Calculate the total volume of the atmosphere.
_________ m^3
2) Calculate the total number of gas molecules in the atmosphere.
________ molecules
3) Calculate the number of gas molecules in Caesar's last breath (37 �C and 1.0 atm).
________ molecules
4) What fraction of all air molecules came from Caesar's last breath?
number _________
5) About how many molecules from Caesar's last breath do you inhale each time you breathe?
________ molecules
Chemistry
1 answer:
IrinaK [193]4 years ago
6 0

Answer:.

Explanation:

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Analysis of a compound indicates that it contians 1.04 g K, 0.70 g Cr, and 0.86 g O. Find its empirical formula.
Annette [7]

Answer:

K2CrO4

Explanation:

To find the empirical formula, we need to divide each element by its atomic mass. The atomic masses of potassium, chromium and oxygen are 39.0983, 51.9961 and 15.999 respectively. We make the divisions as follows:

K = 1.04/39.0983 = 0.027

Cr = 0.70/51.9961 = 0.013

O = 0.86/15.999 = 0.054

We now divide by the smallest which is the number of moles of the Chromium

K = 0.027/0.013 = 2

Cr = 0.013/0.013 = 1

K = 0.054/0.013 = 4 approximately

The empirical formula is thus:

K2CrO4

7 0
3 years ago
During the discussion of gaseous diffusion for enriching uranium, it was claimed that 235UF6 diffuses 0.4% faster than 238UF6. S
Kay [80]

<u>Answer:</u> The below calculations proves that the rate of diffusion of ^{235}UF_6 is 0.4 % faster than the rate of diffusion of ^{238}UF_6

<u>Explanation:</u>

To calculate the rate of diffusion of gas, we use Graham's Law.

This law states that the rate of effusion or diffusion of gas is inversely proportional to the square root of the molar mass of the gas. The equation given by this law follows the equation:

\text{Rate of diffusion}\propto \frac{1}{\sqrt{\text{Molar mass of the gas}}}

We are given:

Molar mass of ^{235}UF_6=349.034348g/mol

Molar mass of ^{238}UF_6=352.041206g/mol

By taking their ratio, we get:

\frac{Rate_{(^{235}UF_6)}}{Rate_{(^{238}UF_6)}}=\sqrt{\frac{M_{(^{238}UF_6)}}{M_{(^{235}UF_6)}}}

\frac{Rate_{(^{235}UF_6)}}{Rate_{(^{238}UF_6)}}=\sqrt{\frac{352.041206}{349.034348}}\\\\\frac{Rate_{(^{235}UF_6)}}{Rate_{(^{238}UF_6)}}=\frac{1.00429816}{1}

From the above relation, it is clear that rate of effusion of ^{235}UF_6 is faster than ^{238}UF_6

Difference in the rate of both the gases, Rate_{(^{235}UF_6)}-Rate_{(^{238}UF_6)}=1.00429816-1=0.00429816

To calculate the percentage increase in the rate, we use the equation:

\%\text{ increase}=\frac{\Delta R}{Rate_{(^{235}UF_6)}}\times 100

Putting values in above equation, we get:

\%\text{ increase}=\frac{0.00429816}{1.00429816}\times 100\\\\\%\text{ increase}=0.4\%

The above calculations proves that the rate of diffusion of ^{235}UF_6 is 0.4 % faster than the rate of diffusion of ^{238}UF_6

3 0
3 years ago
Perform the following operationand express the answer inscientific notation.7.00x10^5 - 5.00x10^4
11Alexandr11 [23.1K]

Taking into account the scientific notation,  the result of the subtraction is 6.5×10⁵.

<h3>Scientific notation</h3>

First, remember that scientific notation is a quick way to represent a number using powers of base ten.

The numbers are written as a product:

a×10ⁿ

where:

  • a is a real number greater than or equal to 1 and less than 10, to which a decimal point is added after the first digit if it is a non-integer number.
  • n is an integer, which is called an exponent or an order of magnitude. Represents the number of times the comma is shifted. It is always an integer, positive if it is shifted to the left, negative if it is shifted to the right.
<h3 /><h3>Subtraction in scientific notation</h3>

You want to subtract two numbers in scientific notation. It should be noted that when the numbers to be added do not have the same base 10 exponent, the base 10 power with the highest exponent must be found. In this case, the highest exponent is 5.

Then all the values ​​are expressed as a function of the base 10 exponent with the highest exponent. In this case: 5.00×10⁴=0.500×10⁵

Taking the quantities to the same exponent, all you have to do is subtract what was previously called the number "a". In this case:

7.00×10⁵ - 0.500×10⁵= (7.00- 0.500)×10⁵= 6.5×10⁵

Finally, the result of the subtraction is 6.5×10⁵.

Learn more about scientific notation:

brainly.com/question/11403716

brainly.com/question/853571

#SPJ1

3 0
2 years ago
The image above shows what happens when hydrochloric acid (HCl) and sodium hydroxide (NaOH) are mixed with water. Which statemen
Sliva [168]
The correct answer is A
6 0
3 years ago
A brown solid<br> element conducts<br> electricity well. Is it a<br> metal or non-metal?
OLga [1]

Answer:

it's a metel

Explanation:

as far as it can conduct electricity.

it's not a metal if it can't except it it's a metalloids

7 0
4 years ago
Read 2 more answers
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