Chemistry (Chapter 1 & 2) Practice HW Questions

A sheet of paper is about 0.0970 mm thick. What is the volume (in cubic inches) of a standard 8.50 in.×11.0 in. sheet of paper? Use the equivalent measure 1 in.=25.4 mm. Round your answer to three decimal places.

0.097 mm×1 in/25.4 mm×8.50 in.×11.0 in.=0.35707 in.3

What is 0.29 km in mm? Report your answer with two significant figures

0.29 km×10^3 m/1 km×10^3 mm/1 m=290,000 mm

Convert a density of 0.345gmL to kilograms per cubic meter.

0.345g/mL×1 kg/1000 g×(100 cm/1 m)^3=345 kg/m^3

A liter is equivalent to:

1 dm cubed 1,000 cm3×(1m/100cm)^3=1×10−3m^3 1 dm^3×(1m/10dm)^3=1×10^−3 m^3 Therefore, 1L=1×10^−3m^3=1dm^3.

Convert a density of 1,235 k/gm3 to grams per cubic centimeter.

1,235kgm3×1000 g/1 kg×(1 m/100 cm)3=1.235g/cm3

Convert 1.000 yard to meters using the equivalent measurement 1 in.=2.54 cm. (Note that this is an exact conversion.)

1.000 yd×36 in./1 yd×2.54 cm/1 in.×1 m/100 cm=0.9144 m

What is the precise mass of the proton?

1.00727 amu

What is the precise mass of the neutron?

1.00866 amu

How many neutrons are in 18 8 O, or oxygen-18?

10 neutrons

Which of the following has 3 significant figures? Select all that apply. 123 12.3 123000. 1.23×104

123 12.3 1.23×104

Through the complete electrolysis of a sample of pure water, a student collects 14.0 grams of hydrogen gas and 112.0 grams of oxygen gas. What mass of water (in grams), if it reacted completely, was initially present? (The electrolysis of water is the use of an electric current to decompose it into its component elements.)

126 grams mass of water = mass of hydrogen gas+mass of oxygen gas

The figure shows a bath tub that holds 40.0gal of water. Complete the volume unit conversion indicated below the figure. Use the equivalent measure 1 gal≈3.785 L. Your answer should have three significant figures (round to the nearest thousand milliliters).

151,000 mL. 40.0 gal×3.785 L1 gal×1000 mL1 L=151,400 mL

Write the formula for an isotope of oxygen with nine neutrons, including the mass number and the atomic number.

17 O 8

The isotopes of hydrogen are often referred to by their common names. Write the chemical formula for the isotope deuterium. Include the mass number and the atomic number. Write the answer in the form XZA using the atomic symbol button in the toolbar, where A is the mass number, Z is the atomic number, and X is the chemical symbol for the unknown element.

2 H 1

A mountain has a height of 2.74 miles. How high is the mountain in meters? Use the fact that 1 mi= 1.609 km. Report your answer to three significant figures.

2.74 mi×1.609 km/1 mi×1000 m/1 km=4408.66 m -> 4410 m

10.3 mL of mercury with a density of 13.56gmL is poured onto a dish with a mass of 125 g and then weighed on a scale. How many grams will the scale read?

265 g m mercury=10.3 mL×13.56gmL=139.668 g m total=139.668 g+125 g=264.668 g≈265 g

Give the result of the following expression with the correct number of significant figures: 84ms×32.533 s=?

2700 m The answer 2732.772 m is rounded to 2 significant figures so the answer is 2700 m.

How many atoms are present in a water molecule?

3

Write the formula for an isotope of hydrogen with two neutrons, including the mass number and the atomic number.

3 H 1

Complete the label on the scale to find an equivalent measure. Use the equivalent measure 1 lb=0.4536 kg. Round your answer to a whole number of grams. 3lbs = how many grams?

3.000 lb×0.4536 kg/ 1 lb×1000 g/ 1 kg=1360.8 g -> 1361 g

Convert a volume of 3.5 m3 to cubic centimeters.

3.5 m^3×(100 cm/1 m)^3=3,500,000 cm^3

Write the chemical formula for the atom that has 15 protons and 16 neutrons. Include the correct atomic symbol, mass number, and atomic number.

31 P 15

Light travels at roughly 3.00×108ms. What is this speed in miles per minute? Use 1mi=1609.344m and 60s=1min. Report your answer in scientific notation with three significant figures. Use the multiplication symbol, ×, rather than the letter x in your answer.

3×10^8m/s×1mi/1609.344m=1.8641×10^5mi/s 1.864×10^5m/s×60s/1min=1.1185×107mi/min -> 1.12×10^7mi/min.

Convert a density of 4,420 k/gm^3 to grams per milliliter.

4,420k/gm^3×1000 g/1 kg×(1 m/100 cm)^3×1 cm^3/1 mL=4.42 g/mL

The density of a cube is 2.0gcm3. If the mass is 128 g, what is the length of each side of the cube? (2 sig figs)

4.0 cm V=md=128g/2.0gcm3=64cm3 length=64 cm3‾‾‾‾‾‾‾√3=4.0 cm

If the accepted value for measurement is 60.3 mL, which of the following set of measurements is precise but not accurate? 56.7 mL, 87.3 mL, 28.9 mL 60.2 mL, 60.3 mL, 60.1 mL 76.5 mL, 76.4 mL, 76.3 mL

56.7 mL, 87.3 mL, 28.9 mL

Write the symbol for an atom with 34 protons and 44 neutrons. Include the mass number and the atomic number.

78 Se 34

Which of the following is NOT a substance made of one type of molecule.

A cell within a human body

A large change in temperature (not resulting from external heating) with the appearance of gas bubbles is most likely an indication of...

A chemical change

Which of the following factors used in a dimensional analysis calculation have a finite number of significant figures (in other words, they are not exact numbers) that might limit the precision of the calculated value?

A measurement of speed equaling (27.7 km/hour)

Units of measurement provide which of the following?

A standard comparison of measurements

Which of the following terms describes the smallest particle of a substance that still retains the chemical properties of that substance?

Atom and Molecule

Which of the following examples is considered a physical change? Select all that apply.

Boiling water, slicing potatoes, and freezing juice are all examples of physical changes because these actions do not alter the chemical composition of the original substance.

What element is used as the standard for the atomic mass unit?

Carbon

How could Antoine Lavoisier, the French scientist credited with proposing the law of conservation of matter, have demonstrated this law?

Carefully measuring the mass of reactants before a reaction and the mass of the products after a reaction in a sealed system

A compound is a chemical substance composed of two or more kinds of elements in a fixed ratio. By what means can the components of a compound be separated?

Chemical means

Which of the following could be considered a physical change?

Chopping firewood simply breaks it into smaller pieces, it does not alter its chemical identity as the other options do. Grass growing seems like it could be a physical change, but it is actually the product of millions of chemical reactions on the cellular level.

Which of the following could be considered a chemical change?

Coal burning Phase changes and mixing of substances are physical processes. When coal burns, carbon atoms form new chemical bonds to oxygen atoms, which is a chemical process.

Who was the first to propose the idea of atoms?

Democritus

Which is an intensive property?

Density

A homogeneous mixture like salt and water can be separated by

Distillation

Intensive properties can be...

Either physical or chemical properties

Which subatomic particle weighs significantly less than 1 amu?

Electron

Which of the following are considered a pure substance? Select all that apply.

Element and Compound

Distinguish between heterogeneous and homogeneous mixtures

Elements, compounds, pure substances

A Toyota Prius Hybrid uses 59.7 L gasoline to drive from San Francisco to Seattle, a distance of 1300 km (two significant digits). What (average) fuel economy, in miles per gallon (mpg), did the Prius get during this trip?

First, you convert the distance from kilometers to miles using the conversion factor, 1 km=0.62137 mi. Second, you convert volume from liters to gallons using the following conversion factors: 1 L=1.0567 qt and 4 qt=1 gallon. Third, you divide the miles that you calculated by the gallons that you calculated to get the average miles per gallon. 51 mpg

When water becomes ice, it undergoes a physical change based on its:

Freezing point

Which element weighs, on average, approximately one atomic mass unit?

Hydrogen

Which of the following observations about a basketball is NOT an example of an intensive property?

It has a mass of 600 grams The mass of the basketball would change if it were smaller, so it is an extensive property. The other examples would not change with changing size.

Choose the best explanation below for why dimensional analysis is also sometimes referred to as the factor label approach.

It is sometimes called the factor label approach because units are treated as a factor (along with a numeric factor) in a quantity like 25g, allowing us to subject the unit to algebraic operations as if they were variables.

Which phase of water has the highest density?

Liquid For water, the liquid phase is more dense than the solid, which is why ice floats. A gas is far less dense, as the particles are very far apart.

Which of the following is an example of a homogeneous mixture?

Maple syrup

Which of the following units is a derived SI unit (not one of the SI base units)? Meter, kilogram, second, or newton?

Newtown

Which of the following events fail to follow the law of conservation of matter? Burning wood for a fire Freezing water into ice cubes The decomposition of MgCl2 into Mg and Cl2

None of these

When a piece of paper is folded into a paper airplane, it undergoes a:

Physical change

Volume, shape, and phase changes are all examples of...

Physical properties

Which of the following is a phase of matter? Select all that apply

Plasma, solid, liquid, gas

What is the first part of a good problem-solving strategy?

Read the question carefully

Which is an intensive property

Recall that an intensive property is a property of matter that is independent of the amount of substance in a sample. The melting point of a substance is an intensive property because it does not depend on the amount of substance present. Heat, volume, and weight are extensive properties because they depend on the amount of substance in a sample.

Which of the following is a rule of significant figures in calculations? Round down if the digit to be dropped is less than 5 Round up if the digit to be dropped is less than 5 Round the result to the same number of digits as the number with the most number of sig figs

Round down if the digit to be dropped is less than 5

0.738×0.28 is 0.20664 but is rounded to 0.21. Which rule or rules are applied to this calculation?

Round the result to the same number of significant figures as the value with the least number of significant figures.

Which of the following can be characterized as a physical change?

Sweat evaporates from your skin Sweating is an example of a phase transition (from liquid to gas) which is a physical change.

Which of the targets represents a data set that is accurate but NOT precise?

Target A shows darts that are close to the bullseye (accurate) but not close to each other (imprecise).

Which of the targets represents a data set that is precise but NOT accurate?

Target B shows darts that are close to each other (precise) but not close to the bullseye (inaccurate).

Which of the targets represents a data set that is both accurate and precise?

Target C shows darts that are both close to each other (precise) and close to the bullseye (accurate).

Which of the following is NOT a likely indicator of a chemical change?

The change in shape of a malleable metal

Which particle contributes neither to the atomic number nor the mass number of an atom?

The electron does not have sufficient mass to be included in the mass number, and only the proton contributes to atomic number.

When reading a measurement from an analog instrument like a ruler or a mercury thermometer, how should you determine the number of significant figures to record?

The least significant figure should be estimated by reading between the smallest markings on the instrument.

The splitting of the nucleus of an atom into smaller components is classified as what type of change?

The nucleus of an atom cannot be split into its components by either a physical or chemical change. Splitting an atom is a nuclear process by which the atom's nucleus undergoes a change.

You examine a substance and generate the following results. Which result describes a chemical property of that substance?

The substance emits a gas when dropped in water If a gas is emitted, this indicates a chemical reaction has occurred, so assessing this reactivity is an example of a chemical property.

Which of the images below shows a physical change?

The water boiling, the ice cream melting, and blowing a bubble are all physical changes because the chemical composition of the substances involved is not changing. In the explosion a chemical change is occuring

A 1.00 m long beam of stainless steel with a square 2.00 cm×2.00 cm cross section has a mass of 3.02 kg. What is its density in grams per cubic centimeter? Round to 2 decimal places

V=1.00 m×100 cm/1 m×2.00 cm×2.00 cm=400 cm m=3.02 kg×1000 g/1 kg=3020 g D=3020g/400 cm3=7.55g/cm3

A cube has a volume of exactly 8L. Find the side lengths in centimeters. Recall that 1 mL=1 cm^3.

V=s^3 s=V‾‾√3 s(in cm)=V(in L)×1000 cm31 L‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾√3 s=8 L×1000 cm31 L‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾√3=8000 cm3‾‾‾‾‾‾‾‾‾√3=20 cm

The density of an unknown crystal is 2.65gmL. If a 4.46 g sample of the crystal is added to a graduated cylinder containing 25.0 mL of water, what will the volume read? Round your answer to one decimal place.

Vc=4.46 g/2.65gmL=1.683 mL Vtot=25.0 mL+1.683 mL=26.683 mL -> 26.7 ml

Which of the following is an example of a physical change?

Wax melting, sugar dissolving in coffee, and steam condensing into water are all examples of physical changes.

In November 2018, the kilogram was redefined in terms of Planck's constant. Before this, the kilogram was based on:

a cylinder of platinum-iridium alloy

When adding numbers, the sum will have:

as many decimal places as the number with fewest decimal places

A sample of magnesium is found to contain 78.70% Mg24 atoms (mass 23.98 amu), 10.13% Mg25 atoms (mass 24.99 amu), and 11.17% Mg26 atoms (mass 25.98 amu). What is the average mass of a magnesium atom?

average mass of magnesium =(0.7870×23.98 amu)+(0.1013×24.99 amu)+(0.1117×25.98 amu) =(18.872+2.531+2.902) amu≈24.31 amu

Naturally occurring chlorine consists of 35Cl (mass 34.96885 amu) and 37Cl (mass 36.96590 amu), with an average mass of 35.453 amu. What is the percent composition of Cl in terms of these two isotopes?

average mass=(fraction of 35Cl×mass of 35Cl)+(fraction of 37Cl×mass of 37Cl) 35.453 amu=(x×34.96885 amu)+[(1.00−x)×36.96590 amu] 35.453amu=34.96885x+36.96590−36.96590x 1.99705x=1.513 = 0.7576 So solving yields: x=0.7576, which means that 1.00−0.7576=0.2424. Therefore, chlorine consists of 75.76% 35Cl and 24.24% 37Cl.

Sugar and water, with appropriate heat, can create caramel. In this example, sugar is undergoing a ___________.

chemical change Sugar and water, when forming caramel, are undergoing a chemical change as the product is different than the reactants

Which of the following is a physical change? Select all that apply. chopping wood bending metal cutting a cake frying an egg

chopping wood, bending metal, cutting a cake

All of the following are extensive properties EXCEPT:

color

An object has a mass of 0.0124kg and a volume of 1893mm3. What is its density in grams per cubic centimeter? Your answer should have three significant figures.

density=0.0124kg/1893mm^3 density=0.0124kg/1893mm^3×1000g/1kg×1000mm^3/1cm^3=6.5505 g/cm^3 -> 6.55 g/cm^3

A homogenous mixture varies from a heterogenous mixture in that a homogenous mixture has properties that:

do not vary in the mixture

Which would NOT be an appropriate unit for density?

g/s

If object A and object B have the same density, but object A has greater mass, then object A must have:

greater volume

When a change in a physical property is observed,

it could be because of a physical change

Leading zeros are only significant if they are:

leading zeros are never significant

To find the number of neutrons in an atom, simply calculate:

mass number - atomic number

Atoms of the same element can have different:

mass numbers

The characteristics of atoms are responsible for the following aspects of a type of matter, EXCEPT:

monetary value

When considering precise mass, which particle has the greatest mass?

neutron

The number of significant figures in a value is a display of the _________ of a measurement. precision accuracy both none of the above

none of the above

A set of measurements that yield very similar results when repeated in the same manner are said to be:

precise

If something is a compound, it is also

pure substance

A homogeneous mixture is also known as a:

solution

What is exactly equal to the total number of protons and neutrons in an atom?

the mass number The number of protons and neutrons in an atom is equal to the atom's mass number. Atomic mass is the average mass of all the isotopes of a certain kind of atom.

If you boil an entire sample of water, the steam that results will have

the same mass as water The law of conservation of matter tells us that mass is conserved as matter changes forms. Therefore, all the water molecules in the steam will have the same mass as when they were in the liquid form.

All of the following are physical properties EXCEPT...

toxicity

When computing using dimensional analysis:

unit conversions can be done either simultaneously or separately