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# Category Archives: Stoichiometry Chemical Calculations

## Percent Yield example question

How many grams of isopentyl alcohol are needed to make 433 grams isopentyl acetate in the reaction given below if the expected yield is 78.5%? Assume the acetic acid is in excess.

CH3COOH + HOCH2CH2CH(CH3)2 → CH3COOCH2CH2CH(CH3)2 + H2O

Solution to this Percent Yield practice problem is given in the video below!

## Limiting Reactants example question

One way to produce hydrogen sulfide gas is by the reaction of iron(II) sulfide with hydrochloric acid:

FeS(s) + 2HCl(aq) → FeCl2(aq) + H2S(g)

If 10.2 g HCl is added to 13.2 g FeS, how many grams of H2S can be formed? What is the mass of the excess reactant remaining?

Solution to this Limiting Reactants practice problem is given in the video below!

## Balancing Chemical Equations example question

Balance the following equations using integral coefficients:

SiCl4 + H2O → SiO2 + HCl

PCl5 + H2O → H3PO4 + HCl

CaO + P4O10 → Ca3(PO4)2

Solution to this Balancing Chemical Equation practice problem is given in the video below!

## Writing Balanced Chemical Equation example problem

Write a balanced equation for the reaction between solid calcium hydroxide and aqueous phosphoric acid to form solid calcium phosphate and water. Include symbols indicating the physical form of each reactant and product.

Solution to this Writing Balanced Equations practice problem is given in the video below!

## Empirical Formula of Compounds example question

Cyclohexanol, used in the manufacture of plastics, has the composition 71.95% C, 12.08% H, and 15.97% O by mass. Determine its empirical formula.

Solution to this Empirical Formula of Compounds practice problem is given in the video below!

## Molecular Formula of Compounds example problem

Ethylene (molecular mass 28.0 u), cyclohexane (84.0 u), and 1-pentene (70.0 u) all have the empirical formula CH2. Give the molecular formula of each compound.

Solution to this Molecular Formula of Compounds practice problem is given in the video below!

## Mass Percent of Elements example question

Calculate the mass percent of each element in ammonium sulfate.

Solution to this Mass Percent of Elements practice problem is given in the video below!

## Molar Mass example question

Determine

(a) the total number of Cl atoms in 125 mL of liquid CCl4 (d = 1.589 g/mL) and

(b) the number of grams of carbon in 215 g of sucrose, C12H22O11 .

Solution to this Molar Mass practice problem is given in the video below!

## Mole & Avogadro’s Number example question

Calculate

a) the mass in mg of  mol Ag and

b) the number of oxygen atoms in 20.5 mol O2

Solution to this Mole & Avogadro Number practice problem is given in the video below!

## Molecular Mass example question

Calculate, to three significant figures, the molecular mass of the following compounds:

1) P4

2) N2O4

3) H2SO4

4) CH3CH2COOH

Solution to this Molecular Mass practice problem is given in the video below!