9. Which sample contains a mole of atoms?
A) 23 g Na
B) 24 g C
C) 42 g Kr
D) 78 g K

Sodium (Na) is the sample that contains a mole of atoms.

Given the following data:

Scientific data:

To determine the sample contains a mole of atoms:

Number of moles = 1.0 moles

Therefore, sodium (Na) is the sample that contains a mole of atoms.

Read more on number of moles here: link

option A. 23g Na

Explanation:

To know which of the options are correct, let's solve each of the options

A. Mass of Na = 23g

MM of Na = 23g/mol.

n = Mass /Molar Mass

n = 23/23 = 1mole

B. Mass of carbon = 24g

MM of carbon = 12g/mol

n = Mass /Molar Mass

n = 24/12 = 2mole

C. Mass of Kr = 42g

MM of Kr = 84g/mol

n = Mass /Molar Mass

n = 42/84 = 0.5mole

D. Mass of K = 78g

MM of K = 39g/mol

n = Mass /Molar Mass

n = 78/39 = 2mole.

From the above illustration, only 23g of Na contains a mole of the atom

first let us lay out the formula for potential

and kinetic energy:

pe = mgh

ke = (mv^2)/2

where: m=mass, v=velocity, g=gravitational

acceleration, h=height

calculating for mass using the known values of

pe:

340j = m (9.81 m/s^2) (50ft) (1m/3.28ft)

m = 2.27 kg

the law of conservation of energy states that

energy is neither created nor destroyed. therefore, the change in kinetic

energy from 50 ft to 35 ft would be equal to the change in potential energy

from 50 ft to 35 ft. however it would be opposite in signs since one is losing

while other is gaining.

ke(35ft) – ke(50ft) = - [ pe(35ft) – pe(50ft]

ke(50ft) = 0 since the brick is initially at rest

ke(35ft) = 340j - 2.27kg (9.81 m/s^2) (35ft)

(1m/3.28 ft)

ke(35ft)

= 102.38 j

it would be d. henry moseley

hope this !

and sorry if i'm late. have a good rest of your day! : d