Estimate the number of electrons contained in 100 g of water. What is the total negative charge of these electrons?

Correct answer: D. 3.35 × 10^ 25 and 5.35 × 10^6 C Molecular mass of water ( H_2O ) is 18 g/mol . Number of moles in 100 g of water is (100)/(18) mol . Number of molecules in 100 g of water is (100)/(18) × 6.022 × 10^ 23 3.345 × 10^ 24 . Each molecule of water ( H_2O ) contains 2 + 8 = 10 electrons. Total number of electrons is 10 × 3.345 × 10^ 24 = 3.345 × 10^ 25 3.35 × 10^ 25 . The magnitude of charge on one electron is 1.6 × 10^ -19 C . Total negative charge is 3.345 × 10^ 25 × 1.6 × 10^ -19 5.35 × 10^6 C .

Concepts Of Physics MCQ Edition [Volume 2]

Exam: Concepts Of Physics MCQ Edition [Volume 2]
Subject: Physics
Chapter: Electric Field and Potential

Concepts Of Physics MCQ Edition [Volume 2] · Physics · Electric Field and Potential

Estimate the number of electrons contained in 100 g of water. What...

Estimate the number of electrons contained in

100 \text{ g}

of water. What is the total negative charge of these electrons?

Options

A $6.02 \times 10^{25}$ and $9.63 \times 10^6 \text{ C}$
B $3.76 \times 10^{25}$ and $6.02 \times 10^6 \text{ C}$
C $3.35 \times 10^{24}$ and $5.35 \times 10^5 \text{ C}$
D $3.35 \times 10^{25}$ and $5.35 \times 10^6 \text{ C}$

Correct answer

D. $3.35 \times 10^{25}$ and $5.35 \times 10^6 \text{ C}$

Step-by-step solution

Molecular mass of water (

H_2O

) is

18 \text{ g/mol}

.

Number of moles in

100 \text{ g}

of water is

\dfrac{100}{18} \text{ mol}

.

Number of molecules in

100 \text{ g}

of water is

\dfrac{100}{18} \times 6.022 \times 10^{23} \approx 3.345 \times 10^{24}

.

Each molecule of water (

H_2O

) contains

2 + 8 = 10

electrons.

Total number of electrons is

10 \times 3.345 \times 10^{24} = 3.345 \times 10^{25} \approx 3.35 \times 10^{25}

.

The magnitude of charge on one electron is

1.6 \times 10^{-19} \text{ C}

.

Total negative charge is

3.345 \times 10^{25} \times 1.6 \times 10^{-19} \approx 5.35 \times 10^6 \text{ C}

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