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

Reading a Periodic TableUsing Dimensional Analysis

Chemistry - Reactions

Aqueous Solutions and states of matterReaction Prediction

Chemistry - Gas Laws

Combined Gas Law: PV = nRT

P is pressureV is volume in litersn is amount of moles of substanceR is a constant - 62.4 (L · mmHg)/(mol · K)T is temperature in Kelvins

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

Substitute:                                                                                                    (740 mmHg)V = (0.117449 mol)(62.4 (L · mmHg)/(mol · K))(293.15 K)Multiply:                                                                                                        (740 mmHg)V = 2148.45 L · mmHgIsolate V:                                                                                                           V = 2.9033 L H₂

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

  remember that hf is only the energy of one photon. not two. not three. one.  1) 5.12 * 10^3 photons  find the energy of one photon, then determine how many photons are needed to reach the sensitivity.  e = hf  = (6.626 * 10^-34 js)(5.95 * 10^19 hz)  = 3.94247 * 10^-14 j per photon  (2.02 * 10^-10 j) / (3.94247 * 10^-14 j/photon) = 5123.69149 photons  round to three sig figs.  2) 5.77 * 10^-17 j  energy of pulse = energy per photon * number of photons  = hfn  = (6.626 * 10^-34 js)(1.66 * 10^13 hz)(5250)  = 5.774559 * 10^-17 j  round to three sig figs.  3) 4.07 * 10^8 kj/mol  10^12 pm = 1 m  c = fλ  f = c/λ  e = hf  = hc/λ  = [(6.626 * 10^-34 js)(3.00 * 10^8 m/s) / (2.94 * 10^-12 m)](1 kj/1000 j)(6.02 * 10^23 photons/mol)  = 40702571.4 kj/mol  round to three sig figs.  4) 9.94 * 10^-1 m  e = hc/λ  λ = hc / e  = (6.626 * 10^-34 js)(3.00 * 10^8 m/s) / (2.00 * 10^-25 j)  = 0.9939 m  round to three sig figs.  5) 9.06 * 10^3 photons  energy of pulse = energy per photon * number of photons  number of photons = energy of pulse / energy per photon  = energy of pulse / (hf)  = (3.87 * 10^-13 j) / [(6.626 * 10^-34 js)(6.45 * 10^16 hz)]  = 9055.23695 photons  round to three sig figs.  6) 2.78 * 10^-15 j  this is problem 1, except in reverse.  sensitivity = minumum number of photons * energy per photon  = (5930)(6.626 * 10^-34 js)(7.077 * 10^14 hz)  = 2.78070758 × 10^-15 j  round to three sig figs.

C. definite shape, definite volume. that is a solid.