CHEM 101 - Exam 1

Determine the neutral formula unit for the compound formed from the ions NH+4 and CO2−3.

(NH4)2CO3

For each element, identify the charge of its most common ion. (Rb)

+1

What is the charge on a hypothetical ion with a 25 protons and 23 electrons

+2

For each element, identify the charge of its most common ion. (Al)

+3

A 9.97 g sample of calcium sulfide was decomposed into its constituent elements, producing 5.54 g of calcium and 4.43 g of sulfur. Which of the statements are consistent with the law of constant composition (definite proportions)? - The mass ratio of Ca to S in every sample of calcium sulfide is 1.25 - The ratio of calcium to sulfur will vary based on how the sample was prepared. - Every sample of calcium sulfide will have 5.54 g of calcium. - The mass percentage of calcium plus the mass percentage of sulfur in every sample of calcium sulfide equals 100%. - Every sample of calcium sulfide will have 55.6% mass of calcium.

- The mass ratio of Ca to S in every sample of calcium sulfide is 1.25 - The mass percentage of calcium plus the mass percentage of sulfur in every sample of calcium sulfide equals 100%. - Every sample of calcium sulfide will have 55.6% mass of calcium.

Arrange the statements made during a process to correspond with the scientific method - The instrument provides evidence that the sample is zinc - You use an instrument to identify elements in the shiny material - You notice a shiny metal speck in a rock - You suspect the tiny spect could be gold - You conclude that the material is zinc

- You notice a shiny metal speck in a rock - You suspect the tiny spect could be gold - You use an instrument to identify elements in the shiny material - The instrument provides evidence that the sample is zinc - You conclude that the sample is zinc

Physical properties

- melting point - boiling point - color - conductivity

Chemical properties

- susceptible to rust - flammability

For each element, identify the charge of its most common ion. Fluorine (F)

-1

For each element, identify the charge of its most common ion. (Se)

-2

Convert 6.91 mL to liters.

0.00691

How many protons are in an ion with 18 electrons and a -1 charge

17 Protons

identify the exact numbers: 3 lbs (the weight of an object measured on a scale) 2.54 cm (the number of centimeters in exactly 1 inch) 56.00 s (the time measured by a stopwatch) 4 choices (the number of choices in a list)

2.54 cm (the number of centimeters in exactly 1 inch) & 4 choices (the number of choices in a list)

Round each number to two significant figures. 233.356: 0.002353: 1.005:

233.356: 2.3x10^2 0.002353: 2.4x10^-3 1.005: 1.0

How many total electrons are in a Fe 2+ ion

24 electrons

Convert 264.9 °F to degrees Celsius.

264.9 °F = 129.4 °C

To how many significant figures should each answer be rounded? equation B: (6.022× 10^23 atoms/mol)(0.801 g)20.18 g/mol =2.390×1022 atoms(unrounded)

3 significant figures

To how many significant figures should each answer be rounded? equation A: (6.626× 10^−34 J⋅s)(2.9979× 10^8 m/s)/4.710×10^−7m =4.217427898089×10^−19 J(unrounded)

4 significant figures

The surface temperature on Mercury has been measured to be 425 K . What is this temperature in degrees Celsius?

425 K = 151.85°C

Convert 6.66 μm to inches.

6.66 μm = 0.0002622

Convert a temperature of 67.0 °C to kelvins.

67.0 °C = 340.15

Convert 9.72 km to centimeters.

972000

Which of the statements about hypotheses and theories is TRUE? A scientific theory summarizes a hypothesis that has been supported with repeated testing. To be called a hypothesis, an explanation must be tested by multiple independent researchers. A hypothesis always leads to a scientific theory. The scientific theory is established first followed by the hypothesis.

A scientific theory summarizes a hypothesis that has been supported with repeated testing.

Name the ionic compound Al2O3

Aluminum oxide

Which of the statements describes a chemical property? Water freezes at 0 ∘C. Iodine (a purple solid) becomes a purple gas. Helium is the lightest monatomic element. Antacid tablets neutralize stomach acid.

Antacid tablets neutralize stomach acid.

Determine the formula: barium phosphate

Ba3(PO4)2

One molecule of caffeine contains 8 atoms of carbon, 10 atoms of hydrogen, 4 atoms of nitrogen, and 2 atoms of oxygen. Write the formula

C8H10N4O2

Write the chemical formula for each compound described. calcium chloride (1Ca ion, 2Cl ions):

CaCl2

Name the ionic compound CaS

Calcium sulfide

CO

Carbon oxide

CoF2(s):

Cobalt(II) Fluoride

CuI(s):

Copper(I) Iodide

copper(I) oxide:

Cu2O

copper(I) bromide:

CuBr

copper(II) bromide:

CuBr2

copper(II) oxide:

CuO

Allotropes of carbon

Diamond fullerenes (buchminsterfullerene) graphite

Proton, neurons, and electrons ___________ have a relative charge of 1-

Electrons

A well-controlled procedure used to obtain data in order to describe a phenomenon.

Experiment

A valid explanation about some natural phenomena

Fact

Anions carry a positive charge.

False

The Cl− and Br− ions have the same number of electrons.

False

The Cu+ and Cu2+ ions have the same number of electrons.

False

When an atom gains an electron, it becomes a cation.

False

iron(III) oxide

Fe2O3

iron(III) oxide:

Fe2O3

iron(III) bromide:

FeBr3

hydrogen gas

H2

water

H2O

Hydrofluoric acid

HF

identify the elements that are diatomic

Hydrogen (H) Nitrogen (N) Oxygen (O) Chlorine (Cl) Fluorine (F) Bromine (Br) Iodine (I)

A statement that can be, but has yet to be, supported by experimental data.

Hypothesis

A tentative model or picture that offers an explanation for the behavior of a reaction

Hypothesis

FeO(s):

Iron(II) Oxide

Fe2O3(s):

Iron(III) Oxide

A generalization that concisely summarizes information about natural phenomena

Law

Write the chemical formula for each compound described. lithium sulfide (2Li ions, 1S ion):

Li2S

Name the ionic compound LiBr

Lithium bromide

Which best describes what happens when molecular compounds melt?

Molecules arranged in a regular pattern change to an irregular pattern.

Classify each of the compounds as molecules or salt NO2 C6H6 CaSO4 KI CH2O CaS

Molecules: NO2, CH2O, C6H6 salt: KI, CaSO4, CaS

A statement describing a natural phenomenon that humans sense.

Observation

lead(IV) bromide:

PbBr4

lead(IV) oxide:

PbO2

Name the ionic compound: K2O

Potassium oxide

Proton, neurons, and electrons __________ have a relative charge of 1+

Protons

A statement that is explained by reproducible experimental data.

Scientific fact

A statement that describes a natural phenomenon by summarizing collected facts.

Scientific law

Identify each transition in this flowchart as a chemical change or a physical change.

See attachment

Name the compound with the chemical formula: SrBr2

Strontium Bromide

Name the compound with the chemical formula: SrO

Strontium Oxide

Name the ionic compound SrCl2

Strontium chloride

SF2

Sulfur difluoride

Which one of the following statements a about scientific hypothesis is FALSE? - The previously known outcome of an observation or experiment can be used as solid proof that a newly-created scientific hypothesis is absolutely true. - A scientific hypothesis is an explanation for a natural phenomenon. - A scientific hypothesis is an educated guess about why something happens. - In order to be useful, a scientific hypothesis must be testable in a way that is replicable by other scientists.

The previously known outcome of an observation or experiment can be used as solid proof that a newly-created scientific hypothesis is absolutely true.

A tentative model that has been tested over and validated over long periods of time

Theory

A scientific theory summarizes a hypothesis that has been supported with repeated testing.

True

The Fe2+ and Fe3+ ions have the same number of protons.

True

The K+ ion is formed when a potassium atom loses one electron.

True

which of the items adopt neither the shape nor volume of its container helium in a balloon soda in a bottle coin in a plastic bag

coin in a plastic bag

Proton, neurons, and electrons _________ have a much lower mass than the other two types of particles

electrons

Label the zeros as significant or not significant in the number 0.020

first: not significant second: not significant third: significant

Which of these substances are elements? silicon lead silicone water quartz iodine

lead silicon iodine

Determine the classes of matter described by each question. Each question may describe more than one class of mater.

molecules arranged in a regular pattern change to an irregular pattern

Identify the power of ten that defines each of these prefixes. Input your answers as 10𝑥 where 𝑥 is the power of ten. nano - centi - milli - kilo - micro - mega -

nano - 10^-9 centi - 10^-2 milli - 10^-3 kilo - 10^3 micro -10^-6 mega - 10^6

Isotopes are atoms of a particular element that contain a different number of _________

neutrons

Proton, neurons, and electrons __________ have no charge

neutrons

Write the names of the metric system units given. Spelling counts. - ng: - mg: - pm: - μm:

ng: nanogram mg: milligram pm: picometer μm: micrometer

Proton, neurons, and electrons ___________ located in the nucleus of an atom

protons and neutrons

P4S3

tetraphosphorus trisulfide

P3N5

triphosphorus pentanitride

Which are examples of matter energy water heat air sound

water; air