Mole Concept Test

Result

Mole Concept Test - 4

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Weekly Quiz Competition

Question 1
1 / -0

The mass of a single atom of an element 'A' is 3.95 x 10^-23g. What is its atomic mass?

A
23.79 u

B
21.79 u

C
0.65 u

D
18.24 u

Solution

The atomic mass of an element is numerically equal to the mass of 1 mole of its atoms.
The mass of one atom of an element A = 3.95 x 10^-23 g

We know that 1 mole of an atom = 6.023 x 10²³ atoms
1 mole of an atom = its atomic mass

Mass of one atom of an element A = 3.95 x 10^-23 g
Mass of 6.023 x 10²³ atoms of an element A = 3.95 x 10^-23 x 6.023 x 10²³ = 23.79 u
Question 2
1 / -0

If one mole of CO and one mole of O₂ are made to react at STP, what is the total number of moles at the end of the reaction?

A
1.5 moles

B
1 mole

C
4 moles

D
2 moles

Solution

The balanced chemical equation of the reaction between CO (g) and O₂ (g) is
2CO (g) + O₂ (g) → 2CO₂ (g)

According to the equation,

The number of moles of CO₂formed = Number of moles of CO used = 1 mole
The number of moles O₂ required = 1/2 number of moles of CO used = 0.5 mole

The number of moles of O₂ left = 1 - 0.5 = 0.5 mole

The total number of moles at the end of the reaction = 1 mole of CO₂+ 0.5 mole of
O₂ = 1.5 moles