Moles
Formulae
Equations
Gases
Solutions
100
True or false: 1 mole of water (H
_{2}
O) contains more molecules than 1 mole of phenol (C
_{6}
H
_{6}
O).
False: mole is like a dozen, and 1 dozen is 1 dozen is 1 dozen!
100
True or false: C
_{4}
H
_{10}
is an empirical formula.
False: the simplest ratio between the elements is 2:5, and the empirical formula is thus C
_{2}
H
_{5}
.
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 (O
_{3}
).
O.
200
Ethanol dissolves in contact with water. Write an equation that describes this transformation.
C
_{2}
H
_{5}
OH
_{(l)}
> C
_{2}
H
_{5}
OH
_{(aq)}
200
What temperature does "STP" refer to?
0 celsius / 273 K.
200
What is M (molar) in SI units?
mol/dm
^{3}
.
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 Al
_{2}
(SO
_{4}
)
_{3}
?
2+3 = 5
300
Write and balance the equation:
Potassium reacts with water to give potassium hydroxide and hydrogen gas.
2K
_{(s)}
+ 2H
_{2}
O
_{(l)}
> 2KOH
_{(aq)}
+ H
_{2(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 KNO
_{3}
dissolves in 100.0 mL of water to give a solution with [KNO
_{3}
] of...
0.0100 mol / 0.1 L = 0.100 M.
400
How many hydrogen *atoms* are in 10.0 moles of ethanol, C
_{2}
H
_{5}
OH?
1 mole ethanol => 6 moles H
10 moles => 60 moles H
60*L => 3.612 x 10
^{25}
400
Which of the following compounds has/have the empirical formula CH
_{2<.sub>O? I: CH3COOH II: C6H12O6 III: C12H22O11}
I & II
400
NH
_{3}
+ HF > NH
_{3}
.HF
34g      34g
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 dm
^{3}
400
Butanol (C
_{4}
H
_{10}
O) 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 FeS
_{2}
. What is its %Fe by mass?
32+32+55.8 = 119.8
55.8 / 119.8 = 46.5%
500
CaCO3 > CaO + CO2
50g       7g (found)
%yield = ?
0.5 mole theoretical yield,
0.5 x 56 = 28
25%
500
Ca
_{(s)}
+ 2H
_{2}
O
_{(l)}
> Ca(OH)
_{2(aq)}
+ H
_{2(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 10
^{19}
= 1.2 x 10
^{20}
ions.
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