Chemistry unit 1 MCQ help

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Irfan Kobber
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2 Which of the following statements is true? The Avogadro constant is the number of
A grams of any element which contains 6.02 × 1023 atoms of that element.
B atoms contained in one mole of any element.
C atoms contained in one mole of any monatomic element.
D particles (atoms, molecules or ions) required to make one gram of a substance


Correct answer is C
Can anyone explain why?
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charco
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(Original post by Irfan Kobber)
2 Which of the following statements is true? The Avogadro constant is the number of
A grams of any element which contains 6.02 × 1023 atoms of that element.
B atoms contained in one mole of any element.
C atoms contained in one mole of any monatomic element.
D particles (atoms, molecules or ions) required to make one gram of a substance


Correct answer is C
Can anyone explain why?
Because there are 6.02 x 1023 atoms in 1 mole of a monatomic element :dontknow:
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Irfan Kobber
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(Original post by charco)
Because there are 6.02 x 1023 atoms in 1 mole of a monatomic element :dontknow:
Why monoatomic? Shouldn't this be any substance?
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username3249896
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(Original post by Irfan Kobber)
Why monoatomic? Shouldn't this be any substance?
It has to be monatomic.

Take CO2. There are 3 x NA atoms in 1 mole of CO2 (NA = the Avogadro constant) since there are NA atoms of C and 2NA atoms of O.

Take X2, a diatomic element. There are 2NA atoms of X in 1 mole of X2.
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Irfan Kobber
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(Original post by BobbJo)
It has to be monatomic.

Take CO2. There are 3 x NA atoms in 1 mole of CO2 (NA = the Avogadro constant) since there are NA atoms of C and 2NA atoms of O.

Take X2, a diatomic element. There are 2NA atoms of X in 1 mole of X2.
I understood but i am still not fully clear about the diatomic part.Could u pls explain it elaborately?
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username3249896
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(Original post by Irfan Kobber)
I understood but i am still not fully clear about the diatomic part.Could u pls explain it elaborately?
Let's take hydrogen gas, H2. This is a diatomic molecule consisting of 2 hydrogen atoms covalently bonded together.

If you have 1 mole of H2, you have 2 moles of H.

In other words, if you have NA molecules of H2, you will have 2NA atoms of H.

Hope this helps
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charco
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(Original post by Irfan Kobber)
I understood but i am still not fully clear about the diatomic part.Could u pls explain it elaborately?
When we say "1 mol of hydrogen" we are referring to the substance hydrogen, which is a diatomic gas.

This means that 1 mol of hydrogen contains 6.02 x 1023 hydrogen molecules.

As each hydrogen molecule contains two atoms there are 1.2 x 1024 hydrogen atoms in 1 mol of hydrogen.
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Irfan Kobber
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Thanks both of you!
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