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Elan Coil [88]
3 years ago
7

Copper has two naturally occurring isotopes. Cu−63 has a mass of 62.939 amu and relative abundance of 69.17%.

Chemistry
1 answer:
fiasKO [112]3 years ago
7 0
The answer is 64.907 amu.

The atomic mass of an element is the average of the atomic masses of its isotopes. The relative abundance of isotopes must be taken into consideration, therefore:
atomic mass of copper = atomic mass of isotope 1 * abundance 1 + atomic mass of isotope 2 * abundance 2

We know:
atomic mass of copper = 63.546 amu
The atomic mass of isotope 1 is: 62.939 amu
The abundance of isotope 1 is: 69.17% = 0.6917
The atomic mass of isotope 1 is: x
The abundance of isotope 2: 100% - 69.17% = 30.83% = 0.3083

Thus:
63.546 amu = 62.939 amu * 0.6917 + x * 0.3083
63.546 <span>amu = 43.535 amu + 0.3083x
</span>⇒ 63.546 amu - 43.535 amu = 0.3083x
⇒ 20.011 amu = 0.3083x
   ⇒ x = 20.011 amu ÷ 0.3083 = 64.907 amu
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Answer:

<em>2.085 x 10^-20 J</em>

<em></em>

Explanation:

minimum energy required to produce photoelectric effect in chromium is given as hf =  7.21 x 10^-19 J

The work function of chromium Ф = 4.37 eV = 7.00151 x 10^-19 J

The minimum energy required to eject an electron from from a chromium metal E = ?

From E = hf - Ф

substituting values, we have

E = (7.21 x 10^-19) - (7.00151 x 10^-19)

E = <em>2.085 x 10^-20 J</em>

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weqwewe [10]

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One mole of nitrogen and one mole of neon are combined in a closed container at STP.How big is the container?V = __________ L
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Answer : The volume of container will be 44.8 L

Explanation :

At STP condition,  

The temperature and pressure are 273 K and 1 atm respectively.

As we know that at STP, 1 mole of substance occupies 22.4 L volume of gas.

As per question,

1 mole of nitrogen gas occupies 22.4 L volume

and,

1 mole of neon gas also occupies 22.4 L volume

Thus, total volume will be:

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Given that sodium chloride is 39.0% sodium by mass, how many grams of sodium chloride are needed to have 100.mg of Na present? G
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<u>Answer:</u> The mass of sodium chloride solution present is 0.256 grams.

<u>Explanation:</u>

We are given:

39.0 % of sodium in sodium chloride solution

This means that 39.0 grams of sodium is present in 100 grams of sodium chloride solution

Mass of sodium given = 100 mg = 0.1 g     (Conversion factor:  1 g = 1000 mg)

Applying unitary method:

If 39 grams of sodium metal is present in 100 grams of sodium chloride solution

So, if 0.1 grams of sodium metal will be present in = \frac{100}{39}\times 0.1=0.256g of sodium chloride solution.

Hence, the mass of sodium chloride solution present is 0.256 grams.

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3 years ago
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