Chem Lab Final

limiting reactant

to find do grams over molar mass and then the lower number is your limiting reactant

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

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)

1

1.0 M (molar) solution contains 1.0 mole of solute per 1.0 L of solution. Which describes a 1.0 mM (millimolar) solution?

1.0 mmole solute per 1.0 L of solution

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)

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

This eperiment involves a decomposition reaction. Which of the follow is true of a decomposition reaction?

A single compound becomes multiple compounds or elements.

What glassware will need to be used in this reaction? Select all that apply

A utility clamp a ring stand a thick-walled combustion tube A utility clamp a ring stand a thick-walled combustion tube

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.

Why was this experiment not intended to be performed as a "wet lab"?

The reagents involved are toxic

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 _____.

Titrant

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.

Based on the data in the graph, which species has the smallest coefficient in the balanced equation?

c Graph starts low and ends high

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

After heating the unknown mixture, the mass of the sample is expected to _____ .

decrease

An endothermic reaction is carried out in a calorimeter. Is the temperature of the water expected to increase, decrease, or stay the same?

decrease

In the titration of a monoprotic acid with a monoprotic base, the point at which the same number of moles of acid and base have been added is called the ______________.

equivalence point

The specific heat of water is 4.184 J/g•°C. What amount of heat, in joules, is required to raise the temperature of 4.90 grams of water from 26.8°C to 46.0°C

on theses to the nearest whole number

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?

q lost = -q gained

Precise determination of the concentration of a solution is called _____

standardization

Analyte

substance analyzed or tested, generally by means of laboratory methods

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. Potassium hydroxide is the ____

titrant

In the procedure, what was the stated purpose of adding nitric acid, HNO3, to the reaction mixture

to assist in the formation of large crystals of lead(II) chromate

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