Moles Review

Chapter 7: ReviewFormulas & Moles

Which of the following is NOT an empirical formula?CH4C3H2N2O4(NH4)2CO3

Answer: N2O4 is NOT an empirical formula because it can be reduced to NO2

What is a possible molecular formula for CH2O?C2H4O2C2H6O2C2H4O3

Answer: C2H4O2 is a possible molecular formula because it will reduce to CH2O

What is the process of converting from moles to grams?

Answer: The conversion will be to multiply by molar mass from periodic table over 1 mol.

What are the oxidation numbers for the elements inCopper (II) sulfate?

CuSO4 is the formulaCu = +2 because of the charge on the metalO= -2 almost always -2 (unless in an elemental state or peroxide)S = +6using the total charge on the compound = 0Cu+2SxO4-8 =0x = +6

What is the oxidation number for carbon in C(diamond)?

C = zeroIn its elemental state (only 1 capital letter), the oxidation number is zero

What is the process for converting from molecules to moles?

Answer: The conversion will be to multiply by 1mol over 6.022x1023molecules (in other words, divide by 6.022x1023molecules)

What is the molar mass of H2O?

Answer: Water has a molar mass of 18.015g/mol

H = 1.008 x 2 = 2.016O = 15.999 x 1= 15.999Then add= 18.015

A raindrop has a mass of 0.050g. How many moles of water are in a raindrop?

Answer: 0.0028mol H2O

0.050g H2O x 1mol/18.015g = 0.00277mol rounds to 0.0028mol

What happens when a hydrated compound is heated?

Answer: The compound loses mass due to the loss of water during heating.

What is the formula for calcium hydroxide?

Answer: Ca(OH)2

If dozen is the unit of measure for donuts, what is the unit of measure for amount of substance?

Answer: mole is the unit of measure for amount of substance

What is the formula for disulfur tetrachloride?

Answer: S2Cl4Prefixes are used for molecular compounds.

What is the formula for acetic acid?

Answer: HC2H3O2no hydro- means polyatomic ion. Acetic comes from acetate.

What is the name for H3P?

Answer: hydrophosphoric acidHydro is required non-polyatomic ions.

What is the name for Fe(OH)3 ?

Answer: iron (III) hydroxideParenthesis required for transition metals. Hydroxide has a -1 charge, but there are 3 of themso Fe is +3.

What is the percent composition of each element in Ca(NO3)2?

Answer: Ca =24.425%N =17.073%O = 58.502%

Ca = 40.078g x 1 = 40.078/164.086*100N = 14.007g x 2 = 28.014/164.086*100O = 15.999g x 6 = 95.994/164.086*100Total = 164.086

A compound was analyzed and found to contain 22.2% nitrogen, 1.60% hydrogen, and 76.2% oxygen. What is the empirical formula of the compound?

Answer: NHO3

22.2gN x 1mol/14.007 = 1.585molN/1.585 = 11.60gH x 1mol/1.008g = 1.587molH/1.585 =176.2gO x 1mol/15.999g = 4.763molO/1.585 = 3.005

A compound composed of hydrogen and oxygen is found to have 0.59g of hydrogen and 9.40g of oxygen. The molar mass of this compound is 34.0g/mol. Find the empirical and molecular formula.

Answer: Empirical = HOMolecular = H2O2

0.59gH x 1mol/1.008g = 0.5853mol/0.5853 = 19.40gO x 1mol/15.999g = 0.5875mol/0.5853 = 1.003

Empirical molar mass = 1.008 + 15.999 = 17.007Molar mass = 34.0g/mol / 17.007 = 22(HO)