Chem 1411 Lab Final review

What is the concentration of a solution of a monoprotic acid (i.e., HA) which required 19.25 mL of 0.0965 M KOH to titrate 15.00 mL of the acid solution? Report the answer with the correct number of significant figures.

0.124 M

When working with very low concentrations, such as 0.000245 M, it can be more convenient to represent the concentration as millimolar instead of as molar, in other words mmol/L instead of mol/L. Which is the correct representation of 0.000245 M as the millimolar concentration?

0.245 mM

When heated, NaOH decomposes according to the following equation. If all of the water is produced as water vapor, what is the expected mass loss for a 5.47 gram sample of NaOH? Report your answer with three significant figures. 2 NaOH (s) → Na2O (s) + H2O (g)

1.23

If 282.4 Joules of heat are added to 32.59 grams of a liquid, raising the temperature of the liquid from 29.7°C to 35.8°C, what is the specific heat capacity of the liquid with units of J/g•°C? Report your answer with 3 significant figures.

1.42

How many millimoles of phosphoric acid (a triprotic acid, H3A) can be completely neutralized by 20.0 mL of 0.252 M potassium hydroxide?

1.68 mmol

Which of the following equations correctly represents the decomposition reaction that occurs when silver(I) oxide is heated?

2 Ag2O (s) → 4 Ag (s) + O2 (g)

A piece of iron (specific heat, 0.444 J/g•°C) is added to 117.94 grams of water (specific heat, 4.184 J/g•°C) in a calorimeter. The water was initially at a temperature of 27.1°C and the iron was initially at 137.6°C. If the final temperature of the system is 33.0°C, what is the mass of the iron?

62.7

How many grams of iron, molar mass 55.85 g/mol, will be consumed during the formation of 11.57 grams of Fe2O3? Report your answer with 3 significant figures. Molar mass of Fe2O3 = 159.69 g/mol 4 Fe + 3 O2 → 2 Fe2O3

8.09

In the following reaction, identify the limiting reactant (note the difference in units: Mg(OH)2 (s)+2 HBr (aq)→MgBr2 (aq)+2 H2O (l)20.0 grams 0.5 mL of 1.0 M

HBr

In the following reaction, identify the limiting reactant: C3H8 (g)+5 O2 (g)→CO2 (g)+2 H2O (g)10.0 mol 20.0 mol

O2

In the following reaction, identify the limiting reactant: C3H8 (g)+5 O2 (g)→CO2 (g)+2 H2O (g)15.0 mol 50.0 mol

O2

Two products are possible in this exchange reaction: PbCrO4 and KNO3. Which precipitate(s)?

PbCrO4

A hot solid is added to a cooler liquid and no reaction takes place, they are simply mixed. The final temperature will ...

always be between the two initial temperatures.

A student performs a titration in order to determine the concentration of a hydrochloric acid solution. Early in the procedure, the flask is not placed directly under the buret and a small amount of the titrant, KOH, drains down the outside of the flask. How will this error affect the calculated value of the HCl concentration?

calculated value < actual value

The color of phenolphthalein changes from __________ to __________ by addition of a base solution as one reaches the neutralization point.

colorless to pink

If the same amount of heat is applied to 10 grams of the following four materials, which will reach the highest temperature?

copper (s), 0.385 J/g•°C

If the lid of the calorimeter is not put in place after the hot metal is added. How will this affect the final temperature of the system?

The final temperature will be lower.

Is the decomposition of KClO3 a physical or chemical change?

Chemical

If you start with a mixture of NaCl and KClO3 that weighs 3.00 g, and the mass of the sample decreases by 0.75 g after heating, what is the best explanation for the change in mass?

0.75 g O2 was formed in the reaction and left the sample as a gas

When heated, iron(III) hydroxide decomposes according to the equation below. When balanced, the coefficient of iron(III) hydroxide is ____. ___ Fe(OH)3 (s) → ___ Fe2O3 (s) + ___ H2O (g)

2

the decomposition of potassium chlorate to form a solid and a gas?

2 KClO3 → 2 KCl + 3 O2

When heated, iron(III) hydroxide decomposes according to the equation below. When balanced, the coefficient of water is ____. ___ Fe(OH)3 (s) → ___ Fe2O3 (s) + ___ H2O (g)

3

How many grams of O2 will be consumed during the formation of 13.10 grams of Fe2O3? Report your answer with 3 significant figures. Molar mass of Fe2O3 = 159.69 g/mol 4 Fe + 3 O2 → 2 Fe2O3

3.94

An acid with molar mass 84.48 g/mol is titrated with 0.650 M KOH. What volume of KOH solution is needed to titrate 1.70 grams of the acid to the equivalence point.

30.96 mL

The specific heat of water is 4.184 J/g•°C. What amount of heat, in joules, is required to raise the temperature of 6.11 grams of water from 22.6°C to 43.4°C? Report your answer with 3 significant figures.

532

Calculate the volume in milliliters of 0.448 M KOH necessary to titrate 0.0254 moles of acetic acid (HOAc, HC2H3O2) to a phenolphthalein end-point. Report the answer with a precision of two decimal places.

56.7

A sample of metal pellets is weighed, heated and then added to a calorimeter containing room temperature water. After adding the majority of the metal sample to the calorimeter, it is discovered that some of the metal was not added and has since cooled. If the cooled portion of metal is now added to the calorimeter and the experiment continues, how will the calculated value of the specific heat be affected?

The calculated value of the specific heat will be lower than it should be.

A potassium hydroxide solution, previously standardized against KHP, is added from a burette to a beaker that contains hydrochloric acid of unknown concentration. One to two drops of phenolphthalein have been added to the acid in the beaker. Hydrochloric acid is the _____.

analyte

The point in a titration at which the indicator changes and the addition of titrant is stopped is called the ______________.

end point

In this experiment, we are able to indirectly determine the heat lost by a hot object by determining the heat gained by a cooler liquid. This is possible because of which thermodynamic relationship?

qlost = -qgained

After carrying out the reaction and filtering and collecting the product, it be more likely to obtain

slightly less than the theoretical amount of product

Four materials and their specific heats are listed below. If samples of each material having the same mass are initially at a temperature of 25°C, which material requires the largest amount of heat to raise its temperature to 35°C?

water (l), 4.184 J/g•°C