Introduction Stoichiometry

Stoichiometry is the branch of chemistry that deals with elements in compounds and with reactants and products in chemical reactions, focusing on

• a. bonding.

• b. energy transfers.

• c. mass relationships.

• d. physical characteristics.

Tags

NGSS.HS-PS1-7

Reaction stoichiometry is based on chemical equations and

• a. the law of conservation of mass.

• b. the ideal gas law.

• c. the law of conservation of momentum.

• d. Avogadro’s number.

The number of significant figures in an answer to a stoichiometry problem is determined only by

• a. the number of significant figures in the mole ratio used to solve the problem.

• b. the number of decimal places in the molar masses of substances in the chemical equation.

• c. the number of significant figures of any measured quantities in the problem.

• d. the number of significant figures in the molar masses of substances in the chemical equation.

The chemical equation P4O10 + 6H2O ® 4H3PO4 can be interpreted correctly as

• a. 1 molecule of P4O10 + 6 molecules of H2O form 4 molecules of H3PO4.

• b. 1 mol of P4O10 + 6 mol of H2O reacts to form 4 mol of H3PO4.

• c. 1 g of P4O10 + 6 g of H2O produces 4 g of H3PO4.

• d. Both (a) and (b)

Tags

NGSS.HS-PS1-7

How many mole ratios can be obtained from the following chemical equation?

Na2S + Cd(NO3)2 ® 2NaNO3 + CdS

• 1

• 4

• 12

• 16

Tags

NGSS.HS-PS1-7

In stoichiometry, molar mass is used to

• a. determine the mole ratio.

• b. balance a chemical equation.

• c. convert the amount in moles of one substance to an amount in moles of another substance.

• d. relate the mass of a substance to the amount in moles of that substance.

Molar mass can be used to relate

• a. mass of reactant to moles of reactant.

• b. moles of product to mass of product.

• c. mass of product to moles of product.

• d. All of the above

In the chemical reaction described by the equation

4Fe(s) + 3O2(g) ® 2Fe2O3(s),

the mole ratio of iron(III) oxide to iron is

• 1:1

• 1:2

• 2:3

• 4:1

Tags

NGSS.HS-PS1-7

What is the unit for the following expression:

mass X 1 mol / molar mass

• a. mol 2 /g

• b. g/mol2

• c. mol

• d. g

In the chemical equation wA + xB ® yC + zD, if you know the

number of moles of A that react, you can determine

• a. the number of moles of each reactant and product.

• b. the number of moles of B only.

• c. the total number of moles of C and D only.

• d. the total number of moles of A and B only.

Tags

NGSS.HS-PS1-7