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Lina20 [59]
3 years ago
7

Is the temperature at which a substance melts the same as the temperature changes from a liquid to a solid

Chemistry
1 answer:
sasho [114]3 years ago
8 0

Answer:

No.

Explanation:

If the temperature changes a substance from it's original form, going from solid to liquid, then the temperature required to change it from a liquid to a solid are the opposite. For example, Ice is Water (H2O) in it's solid form. In order to freeze water into ice, the temperature must be very low. In order to melt the ice back into water, the temperature must be higher than the freezing point, but not too high or it will boil, making it a gaseous substance instead.

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What is orbital theory of bonding in metals
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Metals of Group 1 donate 1 electron from its ns orbital to form ionic bond, where n is the no. of its outermost shell. 
Metals of Group 2<span> donate 2 electrons from its ns orbital to form ionic bond, where n is the no. </span>of its <span>outermost shell. </span>
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1. Which of the following nuclear equations is correctly balanced? (choices attached)
lawyer [7]

1. <em>Balancing nuclear equations </em>

Answer:

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

Explanation:

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.  

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

3.<em> Calculating the half-life </em>

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

7 0
3 years ago
Three students use a meterstick with millimeter markings to measure a length of wire. Their measurements are 3 cm, 3.3 cm, and 2
Volgvan

Answer: 3 cm

Explanation:

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The table above lists the wavelength range, frequency range, possible uses, and hazards of the seven types of electromagnetic
arsen [322]

X-ray

Explanation:

X-rays are used medically by doctors to image the interior of the human body but can cause cell damage.

X-rays are energetic radiations that are classified as ionizing radiations.

They penetrate the skin and body tissues.

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