Chapter 5 Flashcards
(31 cards)
How are the properties of compounds different from their constituent elements?
The properties of a compound are different from the elements that make it up. For example, sugar (C₁₂H₂₂O₁₁) contains carbon, hydrogen, and oxygen, but its physical state and reactivity are different from these elements.
How do the properties of sugar differ from its constituent elements?
Sugar is a solid, non-reactive substance, whereas carbon is a black solid, hydrogen is a flammable gas, and oxygen is a reactive gas.
How do the properties of salt (NaCl) differ from its constituent elements?
Salt is a stable, crystalline solid, whereas sodium is a highly reactive metal, and chlorine is a toxic gas.
What is the test for hydrogen gas?
A burning splint produces a ‘pop’ sound when exposed to hydrogen gas.
What is the test for oxygen gas?
A glowing splint reignites in the presence of oxygen gas.
How is sodium chloride (NaCl) formed?
Sodium (Na) donates an electron to chlorine (Cl), forming Na⁺ and Cl⁻ ions, which attract to form an ionic bond.
What is the difference between an element and a compound?
Elements consist of only one type of atom (e.g., O₂, He, Cu), while compounds contain atoms of different elements bonded together (e.g., H₂O, NaCl, CH₄).
What is the fixed ratio of reactants and products in 2H₂ + O₂ → 2H₂O?
Hydrogen and oxygen react in a 2:1 ratio, forming water in a 2:2 ratio with hydrogen.
Who stated the law of constant composition?
Joseph Proust.
What is the law of constant composition?
A given compound always contains the same proportion of its elements by mass.
What is the oxygen-to-hydrogen mass ratio in water?
8:1.
Why is the law of constant composition also called the law of definite proportions?
Because it states that the ratio of elements in a compound is always fixed.
How is the law of constant composition related to the law of conservation of mass?
The constant composition of compounds is a direct result of the conservation of mass in chemical reactions.
How do you determine the number of atoms in a molecular formula?
By reading the subscripts: H₂SO₄ → 2 H, 1 S, 4 O; Ca(NO₃)₂ → 1 Ca, 2 N, 6 O.
How does changing a subscript in a formula change the compound?
It creates a different compound (e.g., CO vs. CO₂, NO₂ vs. N₂O).
What is the correct order of elements in a compound?
Metals first: NaCl, not ClNa; More metal-like nonmetals first: SiO₂, not O₂Si; Lower elements in a column first: SiC, not CSi.
How many periods and groups are in the periodic table?
7 periods (rows) and 18 groups (columns).
What is a metalloid in period 3?
Silicon (Si).
How do you identify an element using the periodic table?
Atomic number 11: Na; Symbol Co: Cobalt; Atomic mass 30.97 amu: Phosphorus.
Are elements atomic or molecular?
Metals are monoatomic (Cu, Al, Hg, Na). Noble gases are monoatomic (He, Ne, Ar). Seven elements are diatomic: H₂, N₂, O₂, F₂, Cl₂, Br₂, I₂.
Which two elements exist as liquids at room temperature?
Bromine (Br₂) and Mercury (Hg).
What are the colors of Cl₂, Br₂, and I₂?
Chlorine (Cl₂) is yellow-green, bromine (Br₂) is red-brown, iodine (I₂) is dark violet.
How do you name binary molecular compounds?
N₂O → Dinitrogen monoxide; PCl₃ → Phosphorus trichloride.
What is the difference between molecular and ionic compounds?
Molecular: Two or more nonmetals, basic unit is molecules (e.g., C₁₂H₂₂O₁₁). Ionic: Metal + nonmetal, basic unit is formula units (e.g., NaCl).
