Activity 4 - Overcoming Mount Molie

What is the representative particle for this substance?
Ca²⁺

• ion

• formula unit

• molecule

• atom

Answer explanation

The representative particle is ion because the substance is a charged element. The charge (2+) indicates that the element is positively charged.

Which of the following is the representative particle for this substance?
Na₂O

• ion

• formula unit

• molecule

• atom

Answer explanation

The representative particle is formula unit because the substance is an ionic compound.

Ionic compounds are composed of a metallic element and a nonmetallic element. Na₂O is composed of sodium (a metallic element) and oxygen (a nonmetallic element).

What is the representative particle for this substance?
PCl₅

• ion

• formula unit

• molecule

• atom

Answer explanation

The representative particle is molecule because the substance is a covalent compound or a molecular compound.

Covalent compounds are composed of nonmetallic elements. PCl₅ is composed of phosphorus and chlorine, which are both nonmetals.

What is the representative particle for this substance?
Ne

• ion

• formula unit

• molecule

• atom

Answer explanation

The representative particle is atom because the substance is an uncharged element.

How many moles are there in 3 grams of carbon monoxide (CO)? Express your answer in 3 decimal places.

(MM of carbon = 12.011 g/mol ; MM of oxygen = 15.999 g/mol)

Type your answer following this format: 2.578 moles

Answer explanation

To solve for the number of moles given the mass, identify first the given substance & its mass. (3 g CO = ______ mol CO)

Then, solve for the molar mass of the given substance. (The molar mass of CO is 28.01 g/mol.)

Divide the mass of the given substance by its molar mass. (3 g / 28.01 g/mol = 0.107 mol).

What is the mass in grams of 2.5 moles of carbon monoxide (CO)? Express your answer in 3 decimal places.

(MM of carbon = 12.011 g/mol ; MM of oxygen = 15.999 g/mol)

Type your answer following this format: 51.123 grams

Answer explanation

To solve for the mass given the number of moles, identify first the given substance & its number of moles. (2.5 mol CO = ______ g CO)

Then, solve for the molar mass of the given substance. (The molar mass of CO is 28.01 g/mol.)

Multiply the number of moles of the given substance by its molar mass. (2.5 mol x 28.01 g/mol = 70.025 g)

How many particles are there in 4.5 moles of ammonia (NH₃)?

Express your answer in 3 decimal places.

(MM of nitrogen= 14.007 g/mol ; MM of hydrogen = 1.008 g/mol)

Type your answer following this format: 1.512 x 10^23 particles

Answer explanation

To solve for the number of particles given the number of moles, identify first the given substance & its number of moles. (4.5 mol NH₃ = ______ particles NH₃ )

Multiply the number of moles of the given substance by Avogadro's Number (4.5 mol x 6.02 x 10²³ particles/mol = 2.709 x 10²⁴ particles)

How many moles are there in 3.010 x 10²⁴ particles of ammonia (NH₃)?

Express your answer in whole number.

(MM of nitrogen= 14.007 g/mol ; MM of hydrogen = 1.008 g/mol)

Type your answer following this format: 3 moles

Answer explanation

To solve for the number of moles given the number of particles, identify first the given substance & its number of particles. (3.010 x 10²⁴ particles NH₃ = ______ moles NH₃ )

Divide the number of particles of the given substance by Avogadro's Number (3.010 x 10²⁴ particles NH₃ / 6.02 x 10²³ particles/mol = 5 moles)

How many particles are there in 4 grams of hydrogen chloride (HCl)? Express your answer in 3 decimal places.

(MM of hydrogen = 1.008 g/mol ; MM of chlorine = 35.453 g/mol)

Type your answer following this format: 7.125 x 10^23 particles

Answer explanation

To solve for the mass given the number of particles, identify first the given substance & its mass. (4 g HCl = ______ particles HCl)

Then, solve for the molar mass of the given substance. (The molar mass of HCl is 36.461 g/mol.)

Lastly, divide the mass of the given substance by its molar mass and multiply by Avogadro’s Number (4 g / 36.461 g/mol x 6.02 x 10²³ particles/mol = 6.604 x 10²² particles)

What is the mass in grams of 1.686 x 10²⁴ particles of hydrogen chloride (HCl)? Express your answer in 3 decimal places.

(MM of hydrogen = 1.008 g/mol ; MM of chlorine = 35.453 g/mol)

Type your answer following this format: 5.321 grams

Answer explanation

To solve for the number of particles given the mass, identify first the given substance & its number of particles. (1.686 x 10²⁴ particles HCl = ______ g HCl)

Then, solve for the molar mass of the given substance. (The molar mass of HCl is 36.461 g/mol.)

Lastly, divide the number of particles of the given substance by Avogadro’s Number and multiply it by its molar mass. (1.686 x 10²⁴ particles / 6.02 x 10²³ particles/mol x 36.461 g/mol = 102.115 grams)