Quantitative Chemistry

Moles

Formulae

Equations

Gases

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.

200

What is the molar mass of HBr?

80.91 g/mol.

200

Write the empirical formula for ozone (O₃).

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.

300

The chemical formula for guanine is C5H5N5O

Its molar mass is...?

151.13 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) + 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.

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 CH₂O?_{I: CH₃COOH
II: C₆H₁₂O₆
III: C₁₂H₂₂O₁₁}

I & II

400

NH₃ + HF --> NH₃.HF

34g NH3 and 34g of HF

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

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 CaCO3 reacted to give 7g of CaO

%yield = ?

0.5 mole theoretical yield,

0.5 x 56 = 28

25%

500

Ca_(s) + 2H₂O_(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