Moles
Formulae
Equations
Gases
Solutions

100

True or false: 1 mole of water (H2O) contains more molecules than 1 mole of phenol (C6H6O).
False: mole is like a dozen, and 1 dozen is 1 dozen is 1 dozen!

100

True or false: C4H10 is an empirical formula.
False: the simplest ratio between the elements is 2:5, and the empirical formula is thus C2H5.

100

True or false: If we sum up the coefficients on the LHS of a equation, it will always matches the sum of coefficients on the RHS.
False: the species can contain different distribution of elements!

100

True or false: gases can directly transform into either solids or liquids.
True: reverse sublimination and condensation.

100

True or false: if you know the density and volume of a solution, you can find out its concentration.
False: density does not in any way relate to the number of moles in a solution.

200

What is the molar mass of HBr?
80.91 g/mol.

200

Write the empirical formula for ozone (O3).
O.

200

Ethanol dissolves in contact with water. Write an equation that describes this transformation.
C2H5OH(l) -> C2H5OH(aq)

200

What temperature does "STP" refer to?
0 celsius / 273 K.

200

What is M (molar) in SI units?
mol/dm3.

300

(Moderator draws the structure of guanine...)

Its molar mass is...?
151.13 Da
(Da, short for Dalton, is a shorthand for g/mol)

300

What is the total number of ions in Al2(SO4)3?
2+3 = 5

300

Write and balance the equation:

Potassium reacts with water to give potassium hydroxide and hydrogen gas.
2K(s) + 2H2O(l) -> 2KOH(aq) + H2(g)

300

Give one condition when the ideal gas law fails.
Very low temperature, or very high pressure. Both diminishes the large distance otherwise present in gases.

300

1.01 g of KNO3 dissolves in 100.0 mL of water to give a solution with [KNO3] of...
0.0100 mol / 0.1 L = 0.100 M.

400

How many hydrogen *atoms* are in 10.0 moles of ethanol, C2H5OH?
1 mole ethanol => 6 moles H

10 moles => 60 moles H

60*L => 3.612 x 1025

400

Which of the following compounds has/have the empirical formula CH2<.sub>O?

I: CH3COOH
II: C6H12O6
III: C12H22O11
I & II

400

NH3 + HF --> NH3.HF

34g &nbsp &nbsp &nbsp34g

What is the limiting reagent?
2 moles; 1.7 moles. HF is limiting.

400

HF (hydrogen fluoride) has a molar mass of 20.0 g/mol. 10.0 g of HF occupies a volume of ____ at STP.
0.5 mol -> 11.2 dm3

400

Butanol (C4H10O) has a molecular weight of 74.12 g/mol, and a density of 0.810 g/mol.

10.0 mL was pipette into a 100.0 mL volumetric flask, and filled to the mark. What is [BuOH]?
10.0 mL = 8.1 g.

8.1 g = 0.109 mol.

[BuOH] = 1.09M.

500

5 umol (micromole) of a immunoprotein (M = 150,000) weighs ___?
0.150 x 5 = 0.750g.

500

Pyrite (fool's gold) has an empirical formula of FeS2. What is its %Fe by mass?
32+32+55.8 = 119.8

55.8 / 119.8 = 46.5%

500

CaCO3 -> CaO + CO2

50g &nbsp &nbsp &nbsp 7g (found)

%yield = ?
0.5 mole theoretical yield,
0.5 x 56 = 28

25%

500

Ca(s) + 2H2O(l) -> Ca(OH)2(aq) + H2(g)

What is the volume of gas, at STP, produced when 0.400 g of Ca(s) reacts completely with water?
Molar mass = 40 g/mol 0.400/40 = 0.0100 moles = 0.0100 moles => 22400 mL x 0.0100 = 224mL

500

100 mL of a 1.0 mM NaOH solution (MW = 40.0 g/mol) contains ____ ions.
1.0 x 10(-3) M, 0.1 L.

1.0 x 10(-4) moles.

NaOH contains 2 ions (Na+, OH-), and this gives 2.0 x 10-4 moles --> (2.0 x 6.02) x 1019 = 1.2 x 1020 ions.