Question

for the reaction represented by the equation 2na + 2h₂o → 2naoh + h₂, how many grams of sodium hydroxide are produced from 3.0 mol of sodium with an excess of water?
120 g

1. g

240 g
multiple choice 1 point
for the reaction represented by the equation pb(no₃)₂ + 2ki → pbi₂ + 2kno₃, how many moles of lead(ii) iodide are produced from 300. g of potassium iodide and an excess of pb(no₃)₂?
3.61 mol
0.904 mol
11.0 mol

Explanation:

Step1: Calculate moles of KI

Molar mass of KI: \(M = 39.10 + 126.90=166.00\space g/mol\)
Number of moles of KI: \(n=\frac{m}{M}=\frac{300\space g}{166.00\space g/mol}\approx1.807\space mol\)

Step2: Use mole ratio from the reaction equation

From \(Pb(NO_3)_2 + 2KI
ightarrow PbI_2 + 2KNO_3\), mole ratio \(n(PbI_2):n(KI)=1:2\)
So \(n(PbI_2)=\frac{1}{2}n(KI)\)
\(n(PbI_2)=\frac{1}{2}\times1.807\space mol = 0.904\space mol\)

Answer:

B. \(0.904\space mol\)