Question

how much energy is evolved/absorbed (answer is 1 ) when 444 g of nbr₃ is produced ? (answer = 38.5 kj)
n₂ + 3 br₂ → 2 nbr₃ + 44.0 kj
the molar mass of nbr₃ is 253.719 g
2 mol nbr₃
(444 g nbr₃)(----------------) = 3 mol nbr₃
4 g nbr₃

5 kj
6 mol nbr₃ (----------------) = 7 kj
8 mol nbr₃
a. 1 b. 2 c. 3 d. 4 e. 5 f. 253.719 g. 3.38×10⁰
h. 3.26×10³ i. 44.0 j. 1.33×10⁻² k. 9.77×10³ l. 4.44×10²
m. 6.66×10² n. 500.0 o. 556 p. 90.0 q. 3.2852 r. 159.81
s. 28.013 t. 1.750 u. 0.8750 v. 13.0 w. 0.46306 x. 1.3892
y. 24.5 z. 38.5 aa. 2.190 bb. evolved cc. absorbed

Explanation:

Step1: Calculate moles of \(NBr_3\)

$$(444\ g\ NBr_3)\times(\frac{1\ mol\ NBr_3}{253.719\ g\ NBr_3})$$
$$=\frac{444}{253.719}\ mol\ NBr_3\approx1.750\ mol\ NBr_3$$

Step2: Calculate energy evolved

From the reaction \(N_2 + 3Br_2
ightarrow2NBr_3+44.0\ kJ\), for \(2\ mol\ NBr_3\) produced, \(44.0\ kJ\) energy is evolved.
Let \(x\) be the energy evolved for \(1.750\ mol\ NBr_3\)
Set up proportion: \(\frac{x}{1.750\ mol}=\frac{44.0\ kJ}{2\ mol}\)
\(x = 1.750\times\frac{44.0}{2}\ kJ=38.5\ kJ\)

Answer:

1. BB. evolved
2. A. 1
3. T. 1.750
4. F. 253.719
5. I. 44.0
6. T. 1.750
7. Z. 38.5
8. B. 2