MDC CHM 1045L MIDTERM QUESTION BANK

A 2.25g sample of magnesium nitrate contains how many moles of this compound?

0.0152

How many ml of 12 M HCl are required to prepare 500 ml of 6M HCl?

250 ml

Elements in group 1A are known as

Alkali metals

A solution is a mixture:

In which a solid solute is always dissolved in a liquid solvent

If 2.0 ml of 6.0 M HCl is used to make a 500 ml aqueous solution, what is the molarity of the diluted solution?

0.024 M

What is a property of a base?

bitter taste

A neutralization can occur between an acid and a base

True

To 225 ml of 0.80 M solution of KI, a student adds enough water to make 1.0L of a more diluted KI solution. What is the molarity of the new solution?

0.18 M

What is the molarity of a solution containing 8.0 g of solute in 500 mL of solution? Note: formula mass of the solute is 24g

0.67 M

Which of the following are combustion reactions?

1) CH4(g) + O2(g) = CO2(g) + H2O 2) CaO(s) + CO2(g) = CaCO3 3) PbCO3(s) = PbO(s) + CO2(g) 4) CH3OH(l) + O2(g) = CO2(g) + H2O(l) Answer: both 1 & 4

How many moles or carbon dioxide are there in 52.06 g of carbon dioxide?

1.183

The specific gravity of sulfuric acid in a bottle is 1.3. The density of sulfuric acid will be:

1.3

How many molecules of CH4 are in 48.2 g of this compound?

1.81 x 10^24

How many mL of 3M HCl are needed to make 300 mL of 0.1 M of HCl?

10mL

What is the molarity of a solution containing 9.0 moles of solute in 500 mL of solution? Note: formula mass of the solute is 24g

18.0 M

When the equation: Al(NO3)3 + Na2S = Al2S3 + NaNO3 is balanced, the coefficients are

2, 3 , 1, 6

The density of silver is 10.5 g/cm^3. What would be the mass in grams of a piece of silver that occupies a volume of 23.6 cm^3?

248

If the precent (mass/volume) for a solute is 4% and the volume of the solution is 750 ml, what is the mass of solute in solution?

30 g

What is the mass % of carbon in C2H6SO?

30.7

What mass of sucrose, C12H22O11, is needed to make 500 ml of a 0.200 M solution?

34.2 g

What mass of Na2SO4 is needed to make 2.5 L of 2.0 M solution?

710g

Identify the piece of glassware that provides the least precise volume measurement of a liquid

A beaker

When an acid reacts with a base what compounds are formed?

A salt and water

Hydrates results from a process known as

Absorption of water

Most solids

Are dense and incompressible

One of the indicators of a chemical reaction is

Both a formation of gas and a change in color

Increasing the temperature of a solution will generally

Both increase the rate at which a solute dissolves and increase the amount of solute that dissolves

What measuring instrument is used in a titration?

Buret

Holding the temperature constant while adding more solute to a solution that already has solute crystal at the bottom of the container:

Cause more solute crystals to appear at the bottom of the container

Which of the following operations usually makes a substance dissolve faster in a solvent

Crushing the substance into a power Raising the temperature Agitation ALL OF THE ABOVE^

A common lab practice when handling chemicals, is to discard the excess back into the chemical bottle

False

A proper technique for volumetric analysis is to rinse the burette 3 times with the acid

False

If you wear contact lenses, it is recommended that you wear them during an experiment

False

In a chemical change that goes to completion, the reaction stops once the product is formed

False

Insoluble materials are to be discarded in the waste basket after the experiment

False

One equivalent of an acid is the mass of an acid that will donate 2 moles of hydrogen to a base

False

The process of determining the concentration of a solution is called molarity, determined by usage of equivalent amount of volumes

False

When filling a burette, the volume being added must be measured first then added

False

When metals react with other elements, like nonmetals, they enter into a combination in which they gain electrons

False

The temperature of an object can be described as

Heat contained in the object

A combination of sand, salt, and water is an example of a:

Heterogeneous mixture

Which one of the following is often easily separated into its components by simple techniques such as filtering or decanting?

Heterogeneous mixtures

In most measurements, the quality of an object is compared to

It's precision

What is the physical state in which matter has no specific shape but does have a specific volume?

Liquid

The density of an object that floats in water is

Lower than the density of water

What is obtained when phosphoric acid and magnesium hydroxide are mixed?

Magnesium phosphate and water

What are the products are the reaction of one mole of magnesium hydroxide and a mole of sulfuric acid?

MgSO4 + 2H2O

Of the reactions below, which one is a decomposition reaction?

NH4Cl → NH3 + HCl

What does not change when a solution is diluted by the addition of a solvent?

Number of miles of solute

The density of copper is about 8.96 g/ml. This means that a certain mass of copper will:

Occupy a volume that is 8.96 times smaller than the volume occupied by the same mass of water

In a normal reaction, the reactants continue to react with each other until

One of the reactants is completely consumed

In order to obtain accurate results during titration, we must

Perform a rough trial

One possible reason for obtaining a lower than expected yield during an experiment is

Side reaction

When predicting whether a reaction will or will not occur, one of the criteria used is:

Single displacement of a solid

Which of the following is the property of an acid?

Sour taste

Since gases usually have a much lower density, the unit volume is usually

The cm^3

When determining the concentration of an acid during titration, we must consider

The concentration of the base used to titrate

The maximum amount of product in a chemical reaction can be calculated by

The quantities of both reactants and products and their coefficients

164.0 g of a substance occupy a volume of 120.0ml. In relation to water, which statement is true?

The substance will sink in water

A piece of metal is heated, then submerged in cool water. Which statement described what happens?

The temperature of the water will increase, and the temperature of the metal will decrease

An independent variable is one such as

The variable that remains unchanged during the experiment

What is the purpose of a titration?

To determine the concentration of an acid or base

A reactant that is completely consumed is called limiting reagent

True

A suitable indicator will change colors when equivalent amounts of an acid and a base are present

True

Decanting a liquid that is mixed with an insoluble solid can be considered a separate technique

True

Formation of a solid is an indication of a reaction

True

Graphs are useful tools for organizing and displaying experimental data

True

In a chemical change that goes to completion, the quantity of product at that point is the maximum obtainable

True

In order to prepare a standard solution of an acid, a volumetric flask must be used

True

Many ionic compounds left open to the air will absorb water from the atmosphere and firm compounds known as hydrates

True

Normality is the concentration of a solution expressed in terms of the number of equivalents

True

Phenolphthalein is an indicator used to signal the end point of a titration

True

The accuracy of a measurement can be described by means of error and % error

True

The density of an object that floats is less than the density of the liquid in which it's found

True

The reliability of a measurement can be described in terms of its precision and accuracy

True

Volumes being calculated for the experiment can be accurately measured by using a beaker

True

The accuracy of a measurement can be described by

True value

Precision refers to

how close a measured number is to other measured numbers

Accuracy refers to

how close a measured number is to the true value