Chm lab final

A mixture of the above components weighs 1.5 g. The benzoic acid weighed 0.35 g after it was separated. What is the % recovery of benzoic acid.

(0.35 g ÷ 1.5 g) × 100=23.3%

You used 0.5 N sodium hydroxide to titrate an acetic acid sample. You use 9.5 mL of acetic acid solution. It took 8.2 mL of the sodium hydroxide solution to reach the pain in point. What is the normality of the acetic acid solution?

(N acid)= (N base)(volume base)÷(volume acid) (0.5mol/L)(0.0082L)÷(0.0095L)=0.432mol/L

Calculate the molar mass using the ideal gas law.

(gRT)÷(PV)= (g/mol)

Given that 1 g of calcium chloride dehydrate is used in the following reaction CaCL₂°2H₂O + Na₂CO₃ → CaCO₃ + 2NaCl + 2H₂O, find the following. 1) the moles of calcium chloride dihydrate used. 2) the mass (g) of sodium carbonate required. 3) this theoretical yield of calcium carbonate. 4) the % yield for the reaction. 5) If a stoichiometric amount of the calcium dehydrate and sodium carbonate are used is either one a limiting reactant (limiting reagent)? 6) if twice the molar amount of sodium carbonate is used compared to calcium chloride dehydrate, which is the limiting reactant? Which reactants should the theoretical yield be based upon?

1) (1g÷147g/mol)= 0.0068mol 2) (106g/mol)(0.0068mol)=0.7212g 3) (100g/mol)(0.0068mol)=0.68g 4) (actual yield ÷ theoretical yield) × 100 = % yield 5) NO 6) (2mol NaCO₃)÷ (1mol) = 2mol (1mol CaCl₂°2H₂O)÷(1mol) = 1 mol Calcium chloride dehydrated is the limiting reactant.

Compounds will have the same electron group arrangement and molecular shape if all of their electron groups are bonding groups with no lone pairs. For which of these compounds does the electron group arrangement and molecular shape match? 1. PI₃ 2. SiF₄ 3. BeCl₂ 4. H₂O 5. BBr₃ 2, 3, and 5 1, 2, and 3 2, 3, and 4 3, 4, and 5 1, 2, and 5.

2, 3, and 5 These three compounds have electron group arrangements and molecular shapes that match. SiF4 has four bonding groups and no lone pairs, and therefore has a tetrahedral electron group arrangement and molecular shape. BeCl2 has two bonding groups so it has a linear electron group arrangement and molecular shape. BBr3 has three bonding groups so it has a trigonal planar group arrangement and molecular shape.

what is the balanced reaction for making oxygen gas?

2H₂O₂ + (catalyst MnO₂) → 2H₂O + O₂

What does to Titration mean?

A procedure for determining solution concentration by using a known amount of a solution of known concentration to determine the concentration of some other solution.

Name all the lab equipment and explain how the items are used.

Beaker-Measures volume graduated cylinder-Measures volume Erlenmeyer flask- measures volume Stirring rod-mixing substances Porcelain evaporating dish-holds solution to be evaporated. Stands up to high heat Forceps-for picking up tiny items Short stem funnel-for pouring a substance into a small container without spilling Scoopula-for scooping up materials Test tube-hold solids and liquids Test tube holder-securely holds test tubes Test tube brush-cleans materials out of test tubes Test tube rack-Hold several test tubes Wash bottle- controlled spray of liquid holds distilled water Watch glass-covers flask and other containers Wire gauze-used for support and spreading out the heat

Which of the following compounds has bond angles of 109°? CCl₄ PCl₃ BF₃ NOCl NH₃

CCl₄ CCl4 has a tetrahedral electron-group arrangement and all four electron groups are bonding groups, so all the angles are 109°.

Write the balance reaction for acetic acid and sodium hydroxide in the titration.

CH₃COOH + NaOH → CH₃CO₂Na + H₂O

What is limewater?

Ca(OH)₂ dissolved in water

Write the balanced reaction for the precipitate reaction in the "stoichiometry of precipitation reaction" lab.

CaCL₂°2H₂O + Na₂CO₃ → CaCO₃ + 2NaCl + 2H₂O

what was the milky white material that was formed when you breathed into limewater?

Calcium Carbonate Ca(OH)₂ + CO₂ → CaCO₃ + H₂O

Which molecule, H2S or H2Se, has the strong dipolar forces and why? H2S has stronger dipolar forces than H2Se because H2S has greater dipole moment than H2Se since the H-S bond is more polar than the H-Se bond. H2Se has stronger dipolar forces than H2S because H2Se has greater dipole moment than H2S since the H-Se bond is more polar than the H-S bond. H2S has stronger dipolar forces than H2Se because H2S has greater dipole moment than H2Se, since H2S has two lone pairs of electrons and H2Se does not. H2Se has stronger dipolar forces than H2S because H2Se has greater dipole moment than H2S, since H2Se has two lone pairs of electrons and H2S does not. H2Se has stronger dipolar forces than H2S because H2Se has a higher molecular mass than H2S, and molecular mass is the most important factor in determining polarities of molecules.

H2S has stronger dipolar forces than H2Se because H2S has greater dipole moment than H2Se since the H-S bond is more polar than the H-Se bond. Both molecules have a net molecular dipole moment since they both have two lone pairs of electrons, yet H2S is more polar than H2Se since the H-S bond is more polar than the H-Se bond due to a greater electronegativity difference in the H-S bond.

Write the balanced neutralization for hydrochloric acid and sodium hydroxide

HCl + NaOH → NaCl + H₂O

How does temperature usually affect the solubility of a substance?

Heat it Increases the solubility of a substance usually.

Briefly explain how a mixture of benzoic acid, iron, sand, and table salt was separated into the individual components.

Iron-magnet Sand- hot water through filter paper. benzoate acid- cool water through the filter paper. Salt-boiling off remaining water.

Molecules with polar bonds may still be nonpolar if the bond dipole vectors cancel each other. All of these molecules are nonpolar except: NCl₃ BeCl₂ CS₂ CCl₄ Cl₂

NCl₃ Nitrogen trichloride (NCl3) is a polar molecule because nitrogen has a lone pair of electrons, so that the bond dipole vectors in the three nitrogen-chlorine bonds do not cancel each other out.

Arrange the following compounds in the order of increasing polarity. 1. HF 2. H₂Se 3. N₂ 4. H₂S N2 < H2Se < H2S < HF HF < H2Se < N2 < H2S HF < H2S < H2Se < N2 H2Se < H2S < N2 < HF N2 < H2S < H2Se < HF

N₂ < H₂Se < H₂S < HF N2 is a nonpolar molecule, since the two atoms are the same element, making the only bond in the molecule a nonpolar bond. H2Se and H2S are both bent molecules, but the H-S bond is more polar than the H-Se bond. The polarity of the bond in linear HF is the largest.

balanced reaction for a glowing splint was added to a mixture of hydrogen and oxygen gas?

O₂ + 2H₂ + (heat) → 2H₂O

What is the ideal gas law equation and what do the letters represent including the appropriate units?

P=(nRT)÷V P = pressure in atm n = moles in (g)÷(g/mol) R = the ideal gas constant in 0.0821(L×atm)÷(mol×°K) T = temperature in Kelvin V = volume in L

Which of the following compounds has bond angles of 120°? SO₃ AsI₃ BeF₂ NCl₃ CH₄

SO₃ SO3 has three electron groups and all of them are bonding groups. This produces bond angles of 120°.

Defined solution and solute.

Solution-a homogeneous mixture of a solute dissolved in solvent. solute- in a solution, the substance dissolved in the solvent.

SN

Steric number. The number of electron groups

What are the bond angles in hydrogen sulfide (H2S) and what is the explanation for the angle? The bond angles are approximately 105° because this is a bent molecule. The bond angles are exactly 180° because this is a linear molecule. The bond angles are exactly 120° because this is a trigonal planar molecule. The bond angles are approximately 118° because this is a bent molecule. The bond angles are approximately 107° because this is a pyramidal molecule.

The bond angles are approximately 105° because this is a bent molecule. The correct electron dot diagram for H2S shows a total of four electron groups with two lone pairs. Each lone pair causes a 2° compression from the ideal VSEPR angle of 109°.

Valence shell electron pair repulsion (VSEPR) theory is based on which of the following concepts? 1)The concept that electrons in a molecule will repel each other due to their negative charge. 2)The concept that valence electrons repel each other due to their small size. 3)The concept that valence electrons are attracted to protons found in the nucleus of the atom, since electrons are negatively charged while protons carry a positive charge. 4)The concept that electrons are very large particles and occupy a large amount of space inside a molecule. 5)The concept that valence electrons are attracted to the nucleus of an atom and therefore will spread as little as possible from each other.

The concept that electrons in a molecule will repel each other due to their negative charge. Since electrons are negatively charged, each bonding pair represents a region of concentrated negative charge. These bonding pairs of electrons will want as much distance in space from other electron pairs, so these bonds in a molecule will repel other bonds as well as lone pairs of electrons.

To determine the shape of a molecule, the number of electron groups that surround the central atom is counted. Multiple bonds are treated as if they were single bonds while each lone pair of electrons counts as a separate electron group. How many electron groups are there in a molecule of sulfur dioxide, SO2? 1)There are three electron groups. 2)There is one electron group. 3)There are two electron groups. 4)There are four electron groups. 5)There are five electron groups.

There are three electron groups. SO2 has one double bond to an oxygen atom - counted as one electron group, a single bond to a second oxygen atom, and a lone pair of electrons.

What was the Phenolphthalein purpose in the titration?

To indicate when the solution had become BASIC

VSEPR

Valence Shell Electron Pair Repulsion

What is the balanced reaction for making hydrogen gas?

Zn + 2HCl → ZnCl₂ + H₂ Mg + 2HCl → MgCl₂ + H₂

What is the molecular shape of the sulfur dioxide (SO2) molecule? bent linear trigonal planar pyramidal tetrahedral

bent Sulfur dioxide has a total of three electron groups, two of them bonding groups and one lone pair. Three electron groups give a trigonal planar electron group arrangement, but when we describe the shape, the lone pairs are ignored.

What is the shape of the nitrite ion (NO₂⁻)? bent. linear. trigonal planar. pyramidal. tetrahedral.

bent. A bent molecule or ion has two bonding groups and one or two lone pairs. The nitrite ion has two bonding groups and one lone pair.

what happened when you bubbled carbon dioxide into a solution of bromothymol blue?

changed color from green to yellow. Bromothymol blue is a acid indicator.

The polarity of a molecule depends on the polarity of the bonds within the molecules as well as the shape of the molecule. All of the following statements are true concerning the polarity of a molecule EXCEPT: polar molecules have three-dimensional shapes while nonpolar molecules are two-dimensional or flat. molecules with symmetrically arranged polar bonds to the same element are nonpolar because the individual bond dipoles cancel out. linear molecules formed from only two atoms are nonpolar if they are formed from two atoms of the same element. linear molecules formed from only two atoms are polar if they are formed from two atoms of different elements with a difference in electronegativity. molecules with symmetrically arranged polar bonds to different elements are polar as long as the individual bond dipoles do not cancel out.

polar molecules have three-dimensional shapes while nonpolar molecules are two-dimensional or flat. This is NOT a true statement. A molecule may be flat or two-dimensional and still be polar as long as the individual bond dipoles do not cancel each other out.

What is the shape of the bromate ion (BrO₃⁻) pyramidal. linear. bent. trigonal planar. tetrahedral.

pyramidal. A pyramidal shape is used to describe a molecule or ion with four electron groups, where three are bonding groups and one is a lone pair.

When the electron dot structure for an ion is drawn, the number of electrons gained or lost to form the ion must be accounted for in the structure. For example the electron dot structure for the phosphate ion, PO₄⁻³ must include three extra electrons in the 3 charge. What is the molecular shape of the phosphate ion: PO₄⁻³? tetrahedral. linear. bent. trigonal planar. pyramidal.

tetrahedral. A tetrahedral shape is used to describe an atom with four electron groups, none of them being lone pairs, as occurs in the PO43- ion.

What is the molecular shape of the silicon tetrabromide (SiBr4) molecule? tetrahedral. bent. trigonal planar. pyramidal. linear.

tetrahedral. A tetrahedral shape is used to describe an atom with four electron groups.