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3 years ago

How many atoms are in a sample of 68.7 g copper (Cu)?

2 answers:

8 0

Divide the number of grams present in the sample by copper's gram atomic weight to find the number of gram atomic weights present. Then multiply that result by Avogadro's Number: 6.022137 x 10^23 atoms/gram atomic weight.1,200 g/(63.54 g/gram atomic weight) ? 18.885741 gram-atomic weights. Hope this helps.

Helen [10]3 years ago

5 0

First convert grams into moles.
Then convert moles to atoms.

There are 63.546 grams of copper per mole. (This is just copper's atomic weight)
Thus, a 68.7 gram copper sample is (68.7/63.546) mols = 1.081 mols.

There are 6.022 * 10^23 atoms per mol.
6.022 * 10^23 * 1.081 = 6.52 * 10^23

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If 27.3% of a sample of silver-112 decays in 1.52 hours, what is the half-life (in hours to 3 decimal places)?

ICE Princess25 [194]

Answer: The half life of the sample of silver-112 is 3.303 hours.

Explanation:

All radioactive decay processes undergoes first order reaction.

To calculate the rate constant for first order reaction, we use the integrated rate law equation for first order, which is:

$k=\frac{2.303}{t}\log \frac{[A_o]}{[A]}$

where,

k = rate constant = ?

t = time taken = 1.52 hrs

$[A_o]$ = Initial concentration of reactant = 100 g

[A] = Concentration of reactant left after time 't' = [100 - 27.3] = 72.7 g

Putting values in above equation, we get:

$k=\frac{2.303}{1.52hrs}\log \frac{100}{72.7}\\\\k= 0.2098hr^{-1}$

To calculate the half life period of first order reaction, we use the equation:

$t_{1/2}=\frac{0.693}{k}$

where,

$t_{1/2}$ = half life period of first order reaction = ?

k = rate constant = $0.2098hr^{-1}$

Putting values in above equation, we get:

$t_{1/2}=\frac{0.693}{0.2098hr^{-1}}\\\\t_{1/2}=3.303hrs$

Hence, the half life of the sample of silver-112 is 3.303 hours.

6 0

3 years ago

Define the term. Theory

Sonja [21]

Answer:

a supposition or a system of ideas intended to explain something, especially one based on general principles independent of the thing to be explained.

(from goo gle)

A explanation for something that doesn't seem to be answered completely, usually very implausible.

Explanation:

6 0

3 years ago

Estructura molecular del óxido nitroso

lozanna [386]

Answer:

yes

Explanation:

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3 years ago

A container with a fixed volume, filled with hydrogen gas at -104°C and 71.8 K PA is heated until the pressure reaches 225.9 K P

Daniel [21]

Answer:

The correct answer is 532 K

Explanation:

The Gay-Lussac law describes the behavior of a gas at constant volume, by changing the pressure or temperature. When is heated, the change in pressure of the gas is directly proportional to it absolute temperature (in Kelvin or K).

We have the following initial conditions:

P1= 71.8 kPa

T1= -104ºC +273 = 169 K

If the pressure increases until reaching 225.9 kPa (P2), we can calculate the final temperature of the gas (T2) by using the Gay-Lussac derived expression:

P1 x T2 = P2 x T1

⇒T2= (P2 x T1)/P1 = (225.9 kPa x 169 K)/71.8 kPa= 531.7 K ≅ 532 K

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3 years ago

The moon does not have its own _______

True [87]

The correct answer is light...

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3 years ago