How many grams are in 4.5 x 10^22 molecules of Ba(NO2)2

17 g Ba(NO₂)₂

General Formulas and Concepts:

Chemistry

StoichiometryAvogadro's Number - 6.022 × 10²³ atoms, molecules, formula units, etc.

Explanation:

Step 1: Define

4.5 × 10²² molecules Ba(NO₂)₂

Step 2: Define conversion

Molar Mass of Ba - 137.33 g/mol

Molar Mass of N - 14.01 g/mol

Molar Mass of O - 16.00 g/mol

Molar Mass of Ba(NO₂)₂ - 137.33 + 2(14.01) + 4(16.00) = 229.35 g/mol

Step 3: Dimensional Analysis

= 17.1384 g Ba(NO₂)₂

Step 4: Check

We are given 2 sig figs. Follow sig fig rules.

17.1384 g Ba(NO₂)₂ ≈ 17 g Ba(NO₂)₂

5.32 x 10⁻³ M

Explanation:

1) The rate law for a first order reaction is:


r = - d [A] / dt = k[A]


2) When you integrate you get:


[ A] = Ao x e ^(-kt)

Remember that here A is PH₃

3) Plug in the data: Ao = 0.0316M, k = 0.0180 /s, and t = 99s


[PH₃] = 0.0316 M x e ^( - 0.0180/s x 99s) = 5.32 x 10⁻³ M