21. how many molecules are in 18.0 g of h₂o?\n22. how many atoms are in 24.0 g of carbon?\n23. how many…

21. How many molecules are in 18.0 g of H₂O?

Explanation:

Step1: Calculate molar mass of H₂O

The molar mass of H₂O: H has a molar - mass of 1.01 g/mol and O has a molar - mass of 16.00 g/mol. So, $M_{H_2O}=2\times1.01 + 16.00=18.02$ g/mol.

Step2: Calculate number of moles

The number of moles $n=\frac{m}{M}$, where $m = 18.0$ g and $M = 18.02$ g/mol. So, $n=\frac{18.0}{18.02}\approx1.00$ mol.

Step3: Calculate number of molecules

Using Avogadro's number $N_A = 6.022\times10^{23}$ molecules/mol. The number of molecules $N=n\times N_A$. So, $N = 1.00\times6.022\times10^{23}=6.022\times10^{23}$ molecules.

Answer:

$6.022\times10^{23}$ molecules

22. How many atoms are in 24.0 g of carbon?

Explanation:

Step1: Determine molar mass of carbon

The molar mass of carbon $M = 12.01$ g/mol.

Step2: Calculate number of moles

$n=\frac{m}{M}$, with $m = 24.0$ g and $M = 12.01$ g/mol. So, $n=\frac{24.0}{12.01}\approx2.00$ mol.

Step3: Calculate number of atoms

Using Avogadro's number $N_A=6.022\times10^{23}$ atoms/mol. The number of atoms $N=n\times N_A$. So, $N = 2.00\times6.022\times10^{23}=1.2044\times10^{24}$ atoms.

Answer:

$1.2044\times10^{24}$ atoms

23. How many molecules are in 44.0 g of CO₂?

Explanation:

Step1: Calculate molar mass of CO₂

The molar mass of CO₂: C has a molar - mass of 12.01 g/mol and O has a molar - mass of 16.00 g/mol. So, $M_{CO_2}=12.01+2\times16.00 = 44.01$ g/mol.

Step2: Calculate number of moles

$n=\frac{m}{M}$, with $m = 44.0$ g and $M = 44.01$ g/mol. So, $n=\frac{44.0}{44.01}\approx1.00$ mol.

Step3: Calculate number of molecules

Using Avogadro's number $N_A = 6.022\times10^{23}$ molecules/mol. The number of molecules $N=n\times N_A$. So, $N = 1.00\times6.022\times10^{23}=6.022\times10^{23}$ molecules.

Answer:

$6.022\times10^{23}$ molecules

24. How many formula units are in 58.5 g of NaCl?

Explanation:

Step1: Calculate molar mass of NaCl

The molar mass of NaCl: Na has a molar - mass of 22.99 g/mol and Cl has a molar - mass of 35.45 g/mol. So, $M_{NaCl}=22.99 + 35.45=58.44$ g/mol.

Step2: Calculate number of moles

$n=\frac{m}{M}$, with $m = 58.5$ g and $M = 58.44$ g/mol. So, $n=\frac{58.5}{58.44}\approx1.00$ mol.

Step3: Calculate number of formula units

Using Avogadro's number $N_A = 6.022\times10^{23}$ formula units/mol. The number of formula units $N=n\times N_A$. So, $N = 1.00\times6.022\times10^{23}=6.022\times10^{23}$ formula units.

Answer:

$6.022\times10^{23}$ formula units

25. How many atoms are in 63.5 g of copper?

Explanation:

Step1: Determine molar mass of copper

The molar mass of copper $M = 63.55$ g/mol.

Step2: Calculate number of moles

$n=\frac{m}{M}$, with $m = 63.5$ g and $M = 63.55$ g/mol. So, $n=\frac{63.5}{63.55}\approx1.00$ mol.

Step3: Calculate number of atoms

Using Avogadro's number $N_A=6.022\times10^{23}$ atoms/mol. The number of atoms $N=n\times N_A$. So, $N = 1.00\times6.022\times10^{23}=6.022\times10^{23}$ atoms.

Answer:

$6.022\times10^{23}$ atoms

26. How many particles are in 90.0 g of H₂O₂?

Explanation:

Step1: Calculate molar mass of H₂O₂

The molar mass of H₂O₂: H has a molar - mass of 1.01 g/mol and O has a molar - mass of 16.00 g/mol. So, $M_{H_2O_2}=2\times1.01+2\times16.00 = 34.02$ g/mol.

Step2: Calculate number of moles

$n=\frac{m}{M}$, with $m = 90.0$ g and $M = 34.02$ g/mol. So, $n=\frac{90.0}{34.02}\approx2.65$ mol.

Step3: Calculate number of particles

Using Avogadro's number $N_A = 6.022\times10^{23}$ particles/mol. The number of particles $N=n\times N_A$. So, $N = 2.65\times6.022\times10^{23}=1.596\times10^{24}$ particles.

Answer:

$1.596\times10^{24}$ particles

27. Find the number of atoms in 10.0 g of helium.

Explanation:

Step1: Determine molar mass of helium

The molar mass of helium $M = 4.00$ g/mol.

Step2: Calculate number of moles

$n=\frac{m}{M}$, with $m = 10.0$ g and $M = 4.00$ g/mol. So, $n=\frac{10.0}{4.00}=2.5$ mol.

Step3: Calculate number of atoms

Using Avogadro's number $N_A=6.022\times10^{23}$ atoms/mol. The number of atoms $N=n\times N_A$. So, $N = 2.5\times6.022\times10^{23}=1.5055\times10^{24}$ atoms.

Answer:

$1.5055\times10^{24}$ atoms

28. How many molecules are in 180 g of glucose (C₆H₁₂O₆)?

Explanation:

Step1: Calculate molar mass of C₆H₁₂O₆

$M_{C_6H_{12}O_6}=6\times12.01+12\times1.01 + 6\times16.00=180.18$ g/mol.

Step2: Calculate number of moles

$n=\frac{m}{M}$, with $m = 180$ g and $M = 180.18$ g/mol. So, $n=\frac{180}{180.18}\approx1.00$ mol.

Step3: Calculate number of molecules

Using Avogadro's number $N_A = 6.022\times10^{23}$ molecules/mol. The number of molecules $N=n\times N_A$. So, $N = 1.00\times6.022\times10^{23}=6.022\times10^{23}$ molecules.

Answer:

$6.022\times10^{23}$ molecules

29. How many atoms are in 20.0 g of neon gas?

Explanation:

Step1: Determine molar mass of neon

The molar mass of neon $M = 20.18$ g/mol.

Step2: Calculate number of moles

$n=\frac{m}{M}$, with $m = 20.0$ g and $M = 20.18$ g/mol. So, $n=\frac{20.0}{20.18}\approx0.991$ mol.

Step3: Calculate number of atoms

Using Avogadro's number $N_A=6.022\times10^{23}$ atoms/mol. The number of atoms $N=n\times N_A$. So, $N = 0.991\times6.022\times10^{23}=5.968\times10^{23}$ atoms.

Answer:

$5.968\times10^{23}$ atoms

30. How many molecules are in 98.0 g of H₂SO₄?

Explanation:

Step1: Calculate molar mass of H₂SO₄

$M_{H_2SO_4}=2\times1.01+32.07+4\times16.00 = 98.09$ g/mol.

Step2: Calculate number of moles

$n=\frac{m}{M}$, with $m = 98.0$ g and $M = 98.09$ g/mol. So, $n=\frac{98.0}{98.09}\approx1.00$ mol.

Step3: Calculate number of molecules

Using Avogadro's number $N_A = 6.022\times10^{23}$ molecules/mol. The number of molecules $N=n\times N_A$. So, $N = 1.00\times6.022\times10^{23}=6.022\times10^{23}$ molecules.

Answer:

$6.022\times10^{23}$ molecules

31. How many molecules are in 36.0 g of water?

Explanation:

Step1: Calculate molar mass of H₂O

$M_{H_2O}=2\times1.01 + 16.00=18.02$ g/mol.

Step2: Calculate number of moles

$n=\frac{m}{M}$, with $m = 36.0$ g and $M = 18.02$ g/mol. So, $n=\frac{36.0}{18.02}\approx2.00$ mol.

Step3: Calculate number of molecules

Using Avogadro's number $N_A = 6.022\times10^{23}$ molecules/mol. The number of molecules $N=n\times N_A$. So, $N = 2.00\times6.022\times10^{23}=1.2044\times10^{24}$ molecules.

Answer:

$1.2044\times10^{24}$ molecules

32. How many formula units are in 117 g of NaCl?

Explanation:

Step1: Calculate molar mass of NaCl

$M_{NaCl}=22.99 + 35.45=58.44$ g/mol.

Step2: Calculate number of moles

$n=\frac{m}{M}$, with $m = 117$ g and $M = 58.44$ g/mol. So, $n=\frac{117}{58.44}=2.00$ mol.

Step3: Calculate number of formula units

Using Avogadro's number $N_A = 6.022\times10^{23}$ formula units/mol. The number of formula units $N=n\times N_A$. So, $N = 2.00\times6.022\times10^{23}=1.2044\times10^{24}$ formula units.

Answer:

$1.2044\times10^{24}$ formula units