When 7.68 g of zinc react with hydrochloric acid, what volume of hydrogen gas will be collected at 20.00C and 740 mm Hg?

V ≈ 2.9 L H₂

General Formulas and Concepts:

Chemistry - Atomic Structure

Chemistry - Reactions

Chemistry - Gas Laws

Combined Gas Law: PV = nRT

Temperature Conversion: K = °C + 273.15

Explanation:

Step 1: Define

Unbalanced RxN:   Zn (s) + HCl (aq) → ZnCl₂ (aq) + H₂ (g)

Balanced RxN:   Zn (s) + 2HCl (aq) → ZnCl₂ (aq) + H₂ (g)

Given:   7.68 g Zn, 20.00 °C, 740 mmHg

Step 2: Identify Conversions

Kelvin Conversion

Molar Mass of Zn - 65.39 g/mol

Step 3: Convert

Stoichiometry:   = 0.117449 mol H₂

Temp Conversion:   20.00 + 273.15 = 293.15 K

Step 4: Find V

Step 5: Check

We are given 2 sig figs as our lowest. Follow sig fig rules and round.

2.9033 L H₂ ≈ 2.9 L H₂

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