What does the host mean when he says that the acid has "donated a proton" to the water? A.

When hydrochloric acid is dissolved in water, a proton disappears in the chemical reaction.

B.

When hydrochloric acid dissociates, a positive hydrogen atom is accepted by water to form H₃O+.

C.

When hydrochloric acid dissociates, a negative hydrogen atom is accepted by water to form H₃O-.

Option B

Explanation:

As Brønsted-Lowry theory states, acids are the ones that can donate protons.

When a proton is donated, it is released to become medium more acidic.

HCl is a strong acid.

HCl (l) + H₂O (l)  →  H₃O⁺ (aq) +  Cl⁻(aq)

These always reffers to strong acid where the dissociation is 100% completed.

In a weak acid, dissociation is not 100% complete, that's why we have an equilibrium.

HA (l) + H₂O (l)  ⇄  H₃O⁺ (aq) +  A⁻(aq)                   Ka

here we have to get the change of moles on decrease the volume of the reaction in gas phase.

the   per the given options it will decrease by (d) 11-50%

we know, on decreasing the volume of the gas phase reaction the reaction moves to the product side.

the reaction:                     so₂cl₂ (g) = so₂ (g) + cl₂ (g)         total

the moles at equilibrium:   1 - α                 α               α           = 1+α

concentrations:                   1 - α               α               α           = 1 + α

(concentration = moles/volume, as volume is 1 l)

(where α is the degree of dissociation)

now the dissociation constant in terms of concentration is :

=  

or,

or,   = (at v = 1l)

the reaction:                     so₂cl₂ (g) = so₂ (g) + cl₂ (g)         total

the moles at equilibrium:   1 - α                 α               α           = 1+α

concentrations:               (1 - α)/0.5           α/0.5         α/0.5       = (1 + α)/0.5

thus, the dissociation constant in terms of concentration is :

or,  

=  

so, the change of 1 : 1/0.5

or, 1: 2

thus it will decrease by 50%.

or, as per the given options it will decrease by 11-50%

a mercury barometer is a device that uses the physical properties of mercury in a tube to measure barometric pressure. mercury barometers are used for : -

1. measurement of atmospheric pressure  

2. determining the altitude of a place

3. weather forecasting

4. calibration and checking of aneroid barometers

5. application in fluid mechanics

6. measurement of pressure in aircrafts

7. surface weather analysis

8. preparation of barographs

9. usage in physical sciences like physics, astronomy & chemistry

10. preparation of aircraft altimeters

characteristics of mercury barometer : -

1.used to define and measure atmospheric pressure.

2.on the average at sea level the column of mercury rises to a height of about 760 mm.

3.this quantity is equal to 1 atmosphere.

4.it is also known as standard atmospheric pressure.

5.a barometer in which the weight of a column of mercury in a glass tube with a sealed top is balanced against that of the atmosphere pressing on an exposed cistern of mercury at the base of the mercury column, the height of the column varying with atmospheric pressure.