Question

question 3 (1 point)
how many moles of water, h₂o, are present in 75.0 g of h₂o?
4.17 moles
7.50 moles
4.41 moles
75.0 moles
1.35 × 10³ moles
question 4 (1 point)
which one of the following molecular formulas is also the simplest formula?
h₂p₄o₆
c₆h₆
h₂o₂
c₂h₆so
c₆h₆o₂

Explanation:

Step1: Calculate molar mass of \(H_2O\)

Molar mass of \(H = 1\space g/mol\), molar mass of \(O=16\space g/mol\).
Molar mass of \(H_2O=(2\times1 + 16)\space g/mol = 18\space g/mol\)

Step2: Use formula \(n=\frac{m}{M}\)

Given \(m = 75.0\space g\) and \(M = 18\space g/mol\)
\(n=\frac{75.0\space g}{18\space g/mol}\approx4.17\space mol\)

The simplest formula (empirical formula) is the lowest - whole - number ratio of atoms in a compound.
For \(H_2P_4O_6\), the ratio of \(H:P:O = 2:4:6=1:2:3\), so empirical formula is \(HP_2O_3\)
For \(C_6H_6\), ratio \(C:H = 6:6 = 1:1\), empirical formula \(CH\)
For \(H_2O_2\), ratio \(H:O=2:2 = 1:1\), empirical formula \(HO\)
For \(C_2H_6SO\), the ratio of \(C:H:S:O=2:6:1:1\), and it cannot be simplified further.
For \(C_6H_6O_2\), ratio \(C:H:O = 6:6:2=3:3:1\), empirical formula \(C_3H_3O\)

Answer:

4.17 moles