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Eva8 [605]
3 years ago
11

You throw a barbeque for your friends. Before you start the grill, your propane tank has a pressure of 78 psi. When you’re finis

hed grilling, the temperature is 95°F and the propane tank reads 74 psi. Come nighttime the outside temperature drastically decreases to 20°C. What is the pressure of the propane tank at night?
Select one:

a. 16 kPa

b. 485 kPa

c. 107 kPa

d. 2300 kPa
Chemistry
1 answer:
Dvinal [7]3 years ago
4 0

Answer:

b. 485 kPa

Explanation:

Gay-Lussac's law express that the pressure of a gas under constant volume is directly proportional to the absolute temperature. The equation is:

P1T2 = P2T1

<em>P is pressure and T absolute temperature of 1, initial state and 2, final state of the gas</em>

<em>Where P1 = 74psi</em>

<em>T2 = 20°C + 273.15 = 293.15K</em>

<em>P2 = ?</em>

<em>T1 = (95°F -32) * 5/9 + 273.15 = 308.15K</em>

<em />

Replacing:

74psi*293.15K = P2*308.15K

70.4psi

In kPa:

70.4psi * (6.895kPa / 1psi) =

<h3>b. 485 kPa </h3>

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Chemical reactions often involve changes in energy due to the breaking and formation of bonds. Reactions in which energy is released are exothermic reactions, while those that take in heat energy are endothermic.

Explanation:

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3 years ago
1. Which of the following nuclear equations is correctly balanced? (choices attached)
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1. <em>Balancing nuclear equations </em>

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_{18}^{37}\text{Ar} + _{-1}^{0}\text{e} \rightarrow _{17}^{37}\text{Cl}

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The main point to remember in balancing nuclear equations is that the <em>sums of the superscripts</em> (the mass numbers) and the <em>subscripts</em> (the nuclear charges) <em>must balance</em>.

Mass numbers: 37 + 0 = 37; balanced.

Charges: 18 + 1 = 17; balanced

B is <em>wrong</em>. Mass numbers not balanced. 6 +2(1) ≠ 4 + 3.

C is <em>wron</em>g. Mass numbers not balanced. 254 + 4 ≠ 258 + 2(1).

D is <em>wron</em>g. Mass numbers not balanced. 14 + 4 ≠ 17 + 2.

===============

2. <em>Amount remaining </em>

Answer:

D. 5.25 g

Explanation:

The half-life of Th-234 (24 da) is the time it takes for half the Th to decay.  

After one half-life, half (50 %) of the original amount will remain.  

After a second half-life, half of that amount (25 %) will remain, and so on.

We can construct a table as follows:  

  No. of                  Fraction       Amount  

<u>half-lives</u>   <u>t/(da</u>)  <u>remaining</u>  <u>remaining/g</u>  

      1             24            ½                21.0  

      2            48            ¼                10.5  

      3             72           ⅛                 5.25  

      4             96          ¹/₁₆                 2.62  

We see that 72 da is three half-lives, and the amount of Th-234 remaining is 5.25 g.  

===============

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Answer:

a. 2.6 min

Explanation:

The fraction of the original mass remaining is 1.0 g/4.0 g ≈ ¼.

We saw from the previous table that it takes two half-lives to decay to ¼ of the original amount.

2 half-lives = 5.2 min       Divide both sides by 2

  1 half-life = 5.2 min/2 = 2.6 min

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2 years ago
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Answer:

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C = 1

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