If a chemist has 2.3 moles of arsenic that has a molar mass of 74.92g/mol, which would be the best way to find out how many atoms of arsenic are in the sample?

multiply 2.3 bu the molar mass of arsenic.

divide 2.3 by the molar mass of arsenic.

multiply 2.3 by avogadro's number.

divide 2.3 by avogadro's number.

              Multiply 2.3 by Avogadro's Number

                     As we know that 1 mole of any substance contains exactly 6.022 × 10²³ particles which is also called as Avogadro's Number. So in order to calculate the number of particles (Atoms) contained by 2.3 moles of Arsenic (As), we will use following relation,

           Moles  =  Number of Atoms ÷ 6.022 × 10²³ Atoms.mol⁻¹

Solving for Number of Molecules,

           Number of Atoms  =  Moles × 6.022 × 10²³ Atoms.mol⁻¹ **

(**This is your answer)

Putting values,

           Number of Atoms  =  2.3 mol × 6.022 × 10²³ Atoms.mol⁻¹

           Number of Atoms  =  1.38 × 10²⁴ Atoms

Hence,

           There are 1.38 × 10²⁴ Atoms present in 2.3 moles of Arsenic.

answer: c. the experiment shows that the red substance experienced a chemical change.

explanation: chemical change is the change in which chemical composition of the substance changes. physical change is the change in which there is no change in chemical composition.

chemical changes are accompanied by following changes:

a) precipitate formation

b) energy is released or absorbed

c) formation of bubbles

d) change in color

as it is given that the red color has disappeared and there is production of gas, it means the red substance has undergone a chemical change.

e