Chemistry - Practice Problem

[Matter - Practice] Classify color, melting point, and physical state.

Physical properties.

[Matter - Practice] Classify flammability, tendency to rust, and reactivity.

Chemical properties.

[Matter - Practice] Classify melting ice.

Physical change: the state changes, but the substance remains H2O.

[Matter - Practice] Classify iron rusting.

Chemical change: iron is converted into new substances.

[Matter - Practice] Classify saltwater.

A homogeneous mixture, assuming all of the salt is dissolved.

[Matter - Practice] Classify chicken noodle soup.

A heterogeneous mixture because different visible phases are present.

[Matter - Practice] Why can a magnet separate iron filings from a mixture?

Mixture components retain their physical properties, so magnetic iron can be removed physically.

[Matter - Practice] How many total atoms are represented by H2O?

3 atoms: 2 H and 1 O.

[Matter - Practice] How many atoms of each element are in Mg3(PO4)2?

3 Mg, 2 P, and 8 O.

[Matter - Practice] Classify each: oxygen gas, carbon dioxide, air.

Oxygen gas is an element; carbon dioxide is a compound; air is a mixture.

[Measurement - Practice] Is “12 students” exact or inexact?

Exact, if the students were counted.

[Measurement - Practice] Is “12.0 mL” exact or inexact?

Inexact because it is a measurement.

[Measurement - Practice] How many significant figures are in 0.00450?

3 significant figures.

[Measurement - Practice] How many significant figures are in 1007?

4 significant figures.

[Measurement - Practice] How many significant figures are in 72.00?

4 significant figures.

[Measurement - Practice] How many significant figures are clearly shown in 2500 with no decimal point?

Usually 2; write scientific notation to remove ambiguity.

[Measurement - Practice] Write 2500 with three significant figures.

2.50 x 10^3.

[Measurement - Practice] Round 7.8462 to three significant figures.

7.85.

[Measurement - Practice] Round 38,649 to three significant figures.

38,600, or 3.86 x 10^4.

[Measurement - Practice] 4.35677 x 0.0064

0.028; the limiting value has 2 significant figures.

[Measurement - Practice] 5.352 + 1.6

7.0; the answer must be rounded to the tenths place.

[Measurement - Practice] 18.2 / 3.15

5.78; both values allow 3 significant figures.

[Measurement - Practice] 12.11 + 0.3 + 4.567

17.0; the least precise term is in the tenths place.

[Measurement - Practice] Evaluate (106.91 x 0.5184) + (108.90 x 0.4816).

107.87 after completing both products, adding, and rounding at the end.

[Measurement - Practice] Evaluate [(0.9832 - 0.9673) / 0.9832] x 100%.

1.62% after applying subtraction precision first and rounding at the end.

[Measurement - Practice] Write 602200000000000000000000 in scientific notation.

6.022 x 10^23.

[Measurement - Practice] Write 0.000000000300 in scientific notation.

3.00 x 10^-10.

[Measurement - Practice] Convert 4.56 x 10^4 to ordinary notation.

45,600.

[Measurement - Practice] Convert 0.000720 to scientific notation.

7.20 x 10^-4.

[Measurement - Practice] Convert 24 nm to meters.

24 nm x (10^-9 m / 1 nm) = 2.4 x 10^-8 m.

[Measurement - Practice] Convert 0.250 L to gallons using 1 L = 0.265 gal.

0.250 L x 0.265 gal/L = 0.0663 gal.

[Measurement - Practice] Convert 192 cm to feet using 2.54 cm = 1 in and 12 in = 1 ft.

192 cm x (1 in/2.54 cm) x (1 ft/12 in) = 6.30 ft.

[Measurement - Practice] Convert 3.50 km to meters.

3.50 x 10^3 m.

[Measurement - Practice] Convert 640 mg to grams.

0.640 g.

[Measurement - Practice] Convert 25 °C to kelvins.

298 K.

[Measurement - Practice] Convert 310 K to degrees Celsius.

37 °C.

[Measurement - Practice] Convert 425 °F to degrees Celsius.

About 218 °C.

[Measurement - Practice] Convert 425 °F to kelvins.

About 491 K after converting to Celsius and adding 273.

[Measurement - Practice] Find the density of an 18.29 g metal sample with a volume of 7.50 mL.

d = 18.29/7.50 = 2.44 g/mL.

[Measurement - Practice] Find the mass of 60.0 mL of a liquid with density 1.42 g/mL.

m = 1.42 x 60.0 = 85.2 g.

[Measurement - Practice] A metal has mass 63.5 g and density 8.96 g/cm^3. Find its volume.

V = 63.5/8.96 = 7.09 cm^3.

[Atomic Structure - Practice] A neutral atom has Z = 20 and A = 40. Find protons, neutrons, and electrons.

20 protons, 20 neutrons, and 20 electrons.

[Atomic Structure - Practice] An atom has 17 protons and 18 neutrons. Find Z and A.

Z = 17 and A = 35.

[Atomic Structure - Practice] Carbon-12 and carbon-14 differ in what particle?

They differ in neutron count; both contain 6 protons.

[Atomic Structure - Practice] An element is 75.0% isotope-10 and 25.0% isotope-11. Find its average atomic mass.

10(0.750) + 11(0.250) = 10.25 amu.

[Atomic Structure - Practice] Why is average atomic mass usually not a whole number?

It is a weighted average of multiple isotopes rather than the mass number of one atom.

[Atomic Structure - Practice] What is the maximum number of electrons in shell 3?

2(3^2) = 18 electrons.

[Atomic Structure - Practice] How many orbitals and electrons can a 3p subshell hold?

3 orbitals and up to 6 electrons.

[Atomic Structure - Practice] How many orbitals and electrons can a 4d subshell hold?

5 orbitals and up to 10 electrons.

[Atomic Structure - Practice] How many electrons are represented by 1s2 2s2 2p6 3s2 3p5?

17 electrons.

[Atomic Structure - Practice] Is 2p7 a possible subshell entry?

No. A p subshell can hold at most 6 electrons.

[Atomic Structure - Practice] Rewrite 1s2 2s2 2p6 3s2 3p5 in abbreviated form.

[Ne] 3s2 3p5.

[Atomic Structure - Practice] How many valence electrons are in 1s2 2s2 2p4?

6 valence electrons in shell n = 2.

[Atomic Structure - Practice] How many valence electrons are in [Ne] 3s2 3p1?

3 valence electrons.

[Atomic Structure - Practice] Write the ground-state electron configuration for a neutral atom with Z = 7.

1s2 2s2 2p3.

[Atomic Structure - Practice] Write the ground-state electron configuration for a neutral atom with Z = 8.

1s2 2s2 2p4.

[Atomic Structure - Practice] Give the 2p orbital pattern for Z = 8.

2p4 is shown as one paired orbital and two singly occupied orbitals.

[Atomic Structure - Practice] Write the electron configuration for a neutral atom with Z = 13.

1s2 2s2 2p6 3s2 3p1.

[Atomic Structure - Practice] Write the abbreviated configuration for a neutral atom with Z = 17.

[Ne] 3s2 3p5.

[Atomic Structure - Practice] Write the abbreviated configuration for a neutral atom with Z = 23.

[Ar] 4s2 3d3.

[Atomic Structure - Practice] How many occupied orbitals are in 1s2 2s2 2p3?

5 occupied orbitals: one 1s, one 2s, and three 2p orbitals.

[Ionic Bonding - Practice] An ion has 12 protons and 10 electrons. What is its charge?

2+.

[Ionic Bonding - Practice] Write the formula formed from Na+ and O2-.

Na2O.

[Ionic Bonding - Practice] Write the formula formed from Ca2+ and Cl-.

CaCl2.

[Ionic Bonding - Practice] Write the formula formed from Al3+ and S2-.

Al2S3.

[Ionic Bonding - Practice] Write the formula for potassium nitride.

K3N.

[Ionic Bonding - Practice] Write the formula for aluminum chloride.

AlCl3.

[Ionic Bonding - Practice] Name CsF.

Cesium fluoride.

[Ionic Bonding - Practice] Name BaCl2.

Barium chloride.

[Ionic Bonding - Practice] Name Al2S3.

Aluminum sulfide.

[Ionic Bonding - Practice] Determine the iron charge and name FeBr3.

Br- totals 3-, so Fe is 3+; iron(III) bromide.

[Ionic Bonding - Practice] Determine the copper charge and name CuCl.

Cl- requires Cu+; copper(I) chloride.

[Ionic Bonding - Practice] Determine the chromium charge and name CrO3.

Three O2- total 6-, so Cr is 6+; chromium(VI) oxide.

[Ionic Bonding - Practice] Determine the iron charge and name Fe2O3.

Three O2- total 6-, divided between two Fe atoms gives Fe3+; iron(III) oxide.

[Ionic Bonding - Practice] Name Cu2O.

Copper(I) oxide.

[Ionic Bonding - Practice] Name CuO.

Copper(II) oxide.

[Ionic Bonding - Practice] Write the formula for cobalt(II) chloride.

CoCl2.

[Ionic Bonding - Practice] Write the formula for zinc sulfide.

ZnS.

[Ionic Bonding - Practice] Write the formula for calcium nitrate.

Ca(NO3)2.

[Ionic Bonding - Practice] Explain the parentheses in Ca(NO3)2.

Two entire nitrate ions are required to balance Ca2+.

[Ionic Bonding - Practice] Write the formula for aluminum sulfate.

Al2(SO4)3.

[Ionic Bonding - Practice] Write the formula for ammonium phosphate.

(NH4)3PO4.

[Ionic Bonding - Practice] Write the formula for magnesium carbonate.

MgCO3.

[Ionic Bonding - Practice] Write the formula for sodium hydroxide.

NaOH.

[Ionic Bonding - Practice] Name ZnSO4.

Zinc sulfate.

[Ionic Bonding - Practice] Name LiHCO3.

Lithium bicarbonate, also called lithium hydrogen carbonate.

[Ionic Bonding - Practice] Name Cu(NO3)2.

Copper(II) nitrate.

[Ionic Bonding - Practice] Name (NH4)2S.

Ammonium sulfide.

[Ionic Bonding - Practice] Write the formula for calcium phosphate.

Ca3(PO4)2.

[Ionic Bonding - Practice] Write the formula for iron(III) sulfate.

Fe2(SO4)3.

[Ionic Bonding - Practice] Write the formula for ammonium carbonate.

(NH4)2CO3.

[Ionic Bonding - Practice] Write the formula for magnesium hydroxide.

Mg(OH)2.

[Ionic Bonding - Practice] Write the formula for sodium acetate.

NaCH3CO2.

[Ionic Bonding - Practice] Write the formula for lead(IV) oxide.

PbO2.

[Covalent Bonding - Practice] How many valence electrons are available in H2O?

8 total: 2 from H atoms and 6 from O.

[Covalent Bonding - Practice] Describe the Lewis structure of H2O.

H-O-H with two lone pairs on oxygen.

[Covalent Bonding - Practice] Describe the Lewis structure of NH3.

Nitrogen has three N-H single bonds and one lone pair.

[Covalent Bonding - Practice] Describe the Lewis structure of CH4.

Carbon has four C-H single bonds and no lone pairs.

[Covalent Bonding - Practice] How many valence electrons are available in CO2?

16 total.

[Covalent Bonding - Practice] Describe the Lewis structure of CO2.

O=C=O with two lone pairs on each oxygen.