Ttakes 7.21 ⋅ 10 − 19 j of energy to remove an electron from an iron atom. what is the maximum wavelength of light that can do this?

276 nm

Explanation:

The equation relating the energy (E) and the wavelength (λ) of a wave is  

E = (hc)/λ                         Multiply both sides by λ

Eλ = hc                            Divide both sides by E

λ = (hc)/E

h = 6.626 × 10⁻³⁴ J·s

c = 2.998 × 10⁸ m·s⁻¹

E = 7.21 × 10⁻¹⁹ J             Calculate the wavelength

λ = (6.626 × 10⁻³⁴ × 2.998 × 10⁸)/7.21 × 10⁻¹⁹

λ = 2.76 × 10⁻⁷ m = 276 × 10⁻⁹ m = 276 nm

the grams   of   barium that   are in   2.3 x 10^23   atoms of barium   is   52.4 g (answer c)

    calculation

mass = moles   of ba   x molar   mass of ba

  molar mass of ba from periodic table=   137.3 g/mol

  use the   avogadro's law   constant   to   calculate the moles of barium

  that   is     1 mole =   6.02   x 10^23 atoms

                    ? moles = 2.3 x 10^23   atoms

by cross   multiplication

=(1 mole   x 2.3x 10^23 atoms)   / 6.02   x10^23 atoms)=   0.382   moles

mass   is therefore = 137.3   g/mol x 0.382 mol = 52.4 ( answer c)

explanation:

water   molecules stay close to each other through cohesion, the collective action of hydrogen bonds between water molecules. cohesion plants draw water upwards from the root through the stem's transport tubes (xylem) to the leaf. this transport occurs even in large trees and against gravity. transpiration, evaporation of water from plant leaves, creates a tension on water molecules being pulled up from the stem and roots.

water also has high (the attraction of one substance to another) properties because of its polar nature. adhesion of water molecules to plant cell walls counteract gravity while water is transported from roots to leaves.

water exhibits a very high surface tension when compared to other liquids. surface tension is a property of a liquid that holds the surface together and allows it to resist an external force. by capillary action, the water forms concave menisci inside the pores. the high surface tension of water pulls the concavity outwards, generating enough force to lift water from the roots to the leaves of plants.

thus, cohesion, along with adhesion and surface tension creates a capillary action that keeps water molecules interacting and moving through the plants out to the leaf cells.

therefore, option d) is the correct answer.

explanation: