Moles & Stoichiometry Test

The calculation of quantities involved in chemical equations is called _____.

• accuracy and precision

• dimensional analysis

• percent composition

• stoichiometry

Answer explanation

The calculation of quantities in chemical equations is known as stoichiometry. It involves determining the relationships between reactants and products in a chemical reaction.

Tags

NGSS.HS-PS1-7

How many moles of aluminum are needed to react completely with 3.6 mol of FeO? 2Al(s) + 3FeO(s) → 3Fe(s) + Al₂O₃(s)

• 1.2 mol

• 1.8 mol

• 2.4 mol

• 3.6 mol

Answer explanation

From the balanced equation, 2 moles of Al react with 3 moles of FeO. Therefore, for 3.6 moles of FeO, the moles of Al needed are (2/3) * 3.6 = 2.4 mol. Thus, the correct answer is 2.4 mol.

Tags

NGSS.HS-PS1-7

A mole ratio is:

• a fraction

• a ratio

• a conversion factor

• all of the above

Answer explanation

A mole ratio is indeed a fraction (part of a whole), a ratio (comparison of quantities), and a conversion factor (used to convert between units in stoichiometry). Therefore, the correct answer is 'all of the above'.

Tags

NGSS.HS-PS1-7

If I have 2 moles of H₂O, how many liters is that?

• 44.8 L

• 22.4 L

• 6.02 L

• 1 L

Answer explanation

To find the volume of 2 moles of H2O at STP, use the molar volume of a gas, which is 22.4 L per mole. Therefore, 2 moles x 22.4 L/mole = 44.8 L. Thus, the correct answer is 44.8 L.

What is the first step in solving a problem in stoichiometry?

• balance the equation

• convert to moles

• mole ratio

• convert to desired units

Answer explanation

The first step in solving a stoichiometry problem is to balance the equation. This ensures that the number of atoms for each element is equal on both sides, which is essential for accurate mole conversions and calculations.

Tags

NGSS.HS-PS1-7

What SI unit is used to measure the number of representative particles in a substance?

• kilogram

• ampere

• Kelvin

• mole

Answer explanation

The mole is the SI unit used to measure the amount of substance, specifically the number of representative particles, such as atoms or molecules, in that substance. It is a fundamental concept in chemistry.

Tags

NGSS.HS-PS1-7

What is the molar mass of C₆H₆O₆?

• 174.1 g

• 200.0 g

• 288.0 g

• 344.2 g

Answer explanation

To find the molar mass of C6H6O6, sum the atomic masses: C (12.01 g/mol) x 6 + H (1.01 g/mol) x 6 + O (16.00 g/mol) x 6 = 174.1 g/mol. Thus, the correct answer is 174.1 g.

Which of the following is NOT a representative particle?

• atom

• molecule

• ion

• gram

Answer explanation

An ion is a charged particle, while an atom and a molecule are neutral entities. A gram is a unit of mass, not a particle. Therefore, the correct answer is 'gram' as it does not represent a particle.

What is the mass in grams of 2.95 mol C₈H₁₈?

• 0.0512 g

• 19.4 g

• 337 g

• 673 g

Answer explanation

To find the mass of 2.95 mol of C8H18, first calculate its molar mass: C (12.01 g/mol) x 8 + H (1.008 g/mol) x 18 = 114.22 g/mol. Then, multiply by the number of moles: 2.95 mol x 114.22 g/mol = 337 g.

Calculate the % Hydrogen in, NaHCO₃, sodium bicarbonate.

• 43.3%

• .012%

• 0.57%

• 1.20%

Answer explanation

To find the % of hydrogen in NaHCO3, calculate the molar mass: Na (23) + H (1) + C (12) + O (3x16) = 84 g/mol. The % of H = (1/84) x 100 = 1.20%. Thus, the correct answer is 1.20%.