STOIC

Question 1

What is the primary goal of solving quantitative chemical problems?

Answer 1

Apply logical processes to solve quantitative chemical problems

Question 2

What are significant figures?

Answer 2

Digits in a measurement that indicate the certainty of the measurement

Question 3

How do you determine significant figures when a decimal point is present?

Answer 3

Count from the first non-zero digit to the right as significant

Question 4

What rule applies to significant figures in multiplication and division?

Answer 4

The answer contains the same number of significant figures as the measurement with the least significant figures

Question 5

What rule applies to significant figures in addition and subtraction?

Answer 5

The answer has the same number of decimal places as the measurement with the least decimal places

Question 6

What is the relative atomic mass (Ar)?

Answer 6

The average of the masses of an element’s naturally occurring isotopes weighted by their abundances

Question 7

What is relative molecular mass or relative formula mass (Mr)?

Answer 7

The sum of the relative atomic masses of the constituent elements

Question 8

What is Avogadro’s number (NA)?

Answer 8

6.022 x 10^23, the number of particles in one mole of a substance

Question 9

What is the definition of molar mass (M)?

Answer 9

The mass of a substance in grams equal to its relative atomic, molecular or formula mass

Question 10

What does the term ‘amount of substance’ refer to in chemistry?

Answer 10

A measure of the number of moles of a substance present

Question 11

What is the empirical formula?

Answer 11

The simplest whole-number ratio of the atoms present in a compound

Question 12

How is percentage composition by mass determined?

Answer 12

From the chemical formula and relative formula mass of the compound

Question 13

What is a limiting reagent?

Answer 13

The reactant that is in limited supply and determines the amount of product formed

Question 14

What is the definition of concentration in solutions?

Answer 14

A measure of the quantity of solute dissolved in a given quantity of solvent

Question 15

How is molar concentration or molarity commonly expressed?

Answer 15

In moles per liter, abbreviated as M

Question 16

What is the significance of a balanced chemical equation?

Answer 16

It provides the relative reacting amounts or mole ratio of substances

Question 17

Fill in the blank: The mass of 1 mole of a substance is equal to its _______.

Answer 17

Molar mass

Question 18

True or False: The empirical formula and the molecular formula are always the same.

Answer 18

False

Question 19

What is the relationship between the relative molecular mass and the mass of a mole of a substance?

Answer 19

The relative molecular mass expressed in grams equals one mole of that substance

Question 20

What is the effect of significant figures on the final answer in calculations?

Answer 20

The final answer must reflect the precision of the least precise measurement

Question 21

How do you calculate the number of moles from mass?

Answer 21

n = mass (g) / molar mass (g/mol)

Question 22

What is the formula for calculating percentage by mass of an element in a compound?

Answer 22

Percentage by mass = (mass of element in 1 mol of compound / molar mass of compound) x 100

Question 23

What is a standard solution?

Answer 23

A solution with an accurately known concentration.

Question 24

What is the process called when a solution’s concentration is determined by reacting it with another solution of known concentration?

Answer 24

Standardisation.

Question 25

What is a primary standard?

Answer 25

A substance with a high degree of purity, an accurately known formula, stability, availability, and a relatively high molar mass.

Question 26

Why is sodium hydroxide not suitable as a primary standard?

Answer 26

It absorbs moisture and reacts with carbon dioxide, leading to impure samples.

Question 27

What are two examples of substances suitable as primary standards?

Answer 27

* Anhydrous sodium carbonate * Potassium hydrogen phthalate (KHP)

Question 28

What is volumetric analysis?

Answer 28

A technique used to find an unknown concentration of a solution through titration.

Question 29

What is the endpoint of a titration?

Answer 29

The point at which the reactants are in the exact mole ratio as shown in the reaction equation.

Question 30

What is the role of an indicator in a titration?

Answer 30

To visually signal when the endpoint has been reached by changing color.

Question 31

Fill in the blank: A primary standard must have a _______.

Answer 31

[high degree of purity].

Question 32

What is the balanced equation for the reaction between ammonia and hydrochloric acid?

Answer 32

NH3 (aq) + HCl (aq) → NH4Cl (aq).

Question 33

What is the significance of the equivalence point in titration?

Answer 33

It indicates that the reaction is complete and the reactants are present in stoichiometric proportions.

Question 34

Calculate the mass of caustic soda obtained from 1.00 kg of sodium carbonate.

Answer 34

Depends on the stoichiometry of the reaction.

Question 35

What is the percentage by mass of sulfur in sulfuric acid?

Answer 35

Approximately 32.7%.

Question 36

What is the mass of chloride in a 10.0 g sample of canned tuna if 1.433 g of silver chloride is precipitated?

Answer 36

The mass of chloride is calculated based on the stoichiometry of the reaction.

Question 37

What is the empirical formula of a hydrocarbon containing 20.0% hydrogen by mass?

Answer 37

CxHy, where x and y are determined based on the remaining percentage.

Question 38

In the reaction Mg + 2HCl → MgCl2 + H2, identify the limiting reagent when using 2.0 mol of Mg and 4.0 mol of HCl.

Answer 38

Neither, both reactants are in stoichiometric amounts.

Question 39

What mass of uranium is produced when reacting 100 g of uranium tetrafluoride with magnesium?

Answer 39

Depends on the stoichiometry of the reaction.

Question 40

What is the precipitate formed when silver nitrate is reacted with sodium chloride?

Answer 40

Silver chloride (AgCl).

Question 41

What is the weight/volume concentration of a solution containing 45.0 g of KCl in 2.0 L?

Answer 41

2.25 g/100 mL.

Question 42

What is the molarity of sodium hydroxide in a solution of 0.10 mol L-1?

Answer 42

0.10 mol L-1.

Question 43

What mass of solute is required to prepare 100 mL of 0.125 mol L-1 oxalic acid solution?

Answer 43

1.125 g.

Question 44

What volume of concentrated HCl is needed to prepare 500 mL of 1.0 mol L-1 HCl from 11 mol L-1 HCl?

Answer 44

45.5 mL.

Question 45

What is the concentration of hydroxide ions in a solution made from 50 mL of 0.002 mol L-1 calcium hydroxide and 10 mL of 0.010 mol L-1 sodium hydroxide?

Answer 45

Calculated based on total moles and volume.

Question 46

What is the molarity of the potassium permanganate solution standardized with pure iron wire?

Answer 46

Depends on the mass of iron and volume of KMnO4 used.

Question 47

Calculate the percentage of calcium carbonate in impure limestone treated with HCl.

Answer 47

Calculated based on remaining acid after neutralization.

Question 48

What is the percentage of ammonia in cloudy ammonia if 10.213 g was diluted to 250 mL and titrated with hydrochloric acid?

Answer 48

Calculated based on the amount of acid neutralized.

Question 49

What is the molarity of sodium hypochlorite in a cleaning product containing 5.25% weight/volume?

Answer 49

Calculated based on the density and percentage concentration.

Question 50

What is the average titre of sodium hydroxide used to standardise hydrochloric acid?

Answer 50

Calculated based on multiple titrations.

Question 51

What is the concentration of sulfuric acid after titration with sodium hydroxide?

Answer 51

Calculated based on the volume of NaOH used.

Question 52

What is the relationship between the moles of iodine and SO2 in the titration analysis?

Answer 52

Determined from the balanced equation for the reaction.

Question 53

What volume of hydrochloric acid was reacted with the mL aliquot?

Answer 53

20.00 mL

Question 54

What is the molarity of the hydrochloric acid used in the reaction?

Answer 54

0.105 mol L-1

Question 55

How much sodium hydroxide was required to neutralize the leftover acid?

Answer 55

6.45 mL

Question 56

What is the molarity of the sodium hydroxide solution used?

Answer 56

0.0500 mol L-1

Question 57

What percentage of ammonia was calculated in the cloudy ammonia?

Answer 57

33%

Question 58

What is the reaction process for determining the molarity of an iodine solution?

Answer 58

I2 is reduced to I- ions, S2O32- ions are oxidised to S4O62- ions

Question 59

What is the approximate molarity of the iodine solution to be standardized?

Answer 59

0.02 mol L-1

Question 60

What volume of the iodine solution sample is to be titrated?

Answer 60

20 mL

Question 61

What is the average titre expected for the titration procedure?

Answer 61

Approximately 20 mL

Question 62

What is the mass of sodium thiosulfate required for the titration?

Answer 62

33%

Question 63

What is the final calculated mass of sodium thiosulfate required?

Answer 63

1.23 g

Question 64

In the titration reaction, what is produced alongside water when NaOH reacts with H2SO4?

Answer 64

Na2SO4

Question 65

What is the molarity of the sulfuric acid used in the reaction?

Answer 65

0.0877 M

Question 66

What was the calculated molarity of a solution in one of the answers?

Answer 66

0.00774 M

Question 67

What is the total mass of sodium chloride produced in the reaction?

Answer 67

84.4 g

Question 68

What is the concentration of a solution that has 5.0 g/100 mL?

Answer 68

5.0 g/100 mL

Question 69

Calculate the percentage yield if the actual yield is 49.0 g.

Answer 69

85%

Question 70

Fill in the blank: The molarity of a solution that has a concentration of 1.2 mol L-1 is _____ mol L-1.

Answer 70

1.2 mol L-1

Question 71

True or False: The average titre for the iodine solution titration is expected to be 40 mL.

Answer 71

False

Question 72

What is the calculated yield of a reaction if the mass produced is 4.96x10-4 mol?

Answer 72

4.96x10-4 mol