A beam of electrons (m = 9.11 × 10-31 kg/electron) has an average speed of 1.9 × 108 m/s. What is the wavelength of electrons having this average speed, in picometers?

12 pm

Explanation:

Step 1: Given data

Step 2: Calculate the kinetic energy (E) of an electron

We will use the following expression.

E = 1/2 × m × v²

E = 1/2 × 9.11 × 10⁻³¹ kg × (1.9 × 10⁸ m/s)²

E = 1.6 × 10⁻¹⁴ J

Step 3: Calculate the wavelength of an electron

We will use the following expression.

E = h × c / λ

λ = h × c / E

λ = 6.63 × 10⁻³⁴ J.s × 3.00 × 10⁸ m/s / 1.6 × 10⁻¹⁴ J

λ = 1.2 × 10⁻¹¹ m

Step 4: Convert "λ" to picometers

We will use the relationship 1 m = 10¹² pm.

1.2 × 10⁻¹¹ m × (10¹² pm/1 m) = 12 pm

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

in chemistry, adhesion and cohesion are attractive forces that exist between molecules. they hold the molecules together from each other. they are different in that adhesive force exists between molecules of different substance while cohesive force happens between molecules of same substance.

adhesion between water and glass causes water molecules at the edge of water and glass interface to climb up the wall in a narrow glass tube. this is called capillary action. cohesion is what gives glass its shape and causes water to form a droplet.