Chemical Changes And Structure - multiple choice Flashcards
A-Aluminium B-Boron C-Chlorine D-Hydrogen E-Phosphorous F-Silicon
a) Identify the element which is a discrete molecular solid at room temperature and pressure
b) Identify the TWO elements which combine to form the compound with the most covalent character
a) E - as only two elements are discrete molecular solids at room temperature in the first twenty elements (phosphorous and sulphur)
b) D and E - most covalent character means smallest difference in electronegativities and both these elements have an electronegativity of 2.2
Which of the following exist as discrete molecules?
A - boron
B - carbon (diamond)
C - silicon
D - sulphur
D - only phosphorus and sulphur are discrete
An element (melting point above 3000'C) forms an oxide which is a gas at room temperature. Which type of bonding is likely to be present in the element?
A - metallic
B - polar covalent
C - non-polar covalent
D - ionic
C - can’t be metallic or ionic as it is about elements and can’t be polar because…
The two hydrogen atoms in a molecule of hydrogen are held together by …
A - hydrogen bond
B - polar covalent bond
C - non-polar covalent bond
D - van der Waals’ forces
C - talking about bonds not forced of attraction so not D and hydrogen bonding only happens between hydrogen and oxygen, fluorine or nitrogen. Both atoms have same electronegativities therefore non-polar
What type of bonding and structure is found in a fullerene?
A - ionic lattice
B - metallic lattice
C - covalent network
D - covalent molecular
D - non-metal to bon-metal is covalent and it’s in a spherical shape so molecular
Element X was found to have the following properties
i) does not conduct electricity when solid
ii) forms a gaseous oxide
iii) solid at room temperature
Element X could be
A - magnesium
B - silicon
C - nitrogen
D - sulphur
D - magnesium is liquid at room temp
- silicon dioxide is sand so solid not gaseous oxide
- nitrogen is gas at room temp
- can only be sulphur
Which of the following does NOT contain covalent bonds?
A - hydrogen gas
B - helium gas
C - nitrogen gas
D - solid sulphur
B - helium is monotomic so makes no bonds
Which type of bond is broken when ice is melted?
A - ionic
B - polar covalent
C - hydrogen
D - non-polar covalent
C - because H—O bonds = hydrogen bonds
The shapes of some common molecules are shown below and each contain at least one polar bond - which molecule is non-polar?
A - H—Cl
B - O
/ \
H H
C - O=C=O
D - H
|
C
/ | \
Cl Cl Cl
C - polar bond because joined to different electronegativities
- symmetrical
- therefore non-polar
A metal (melting point 843'C, density 1.54g cm^-3) was obtained by electrolysis of its chloride (melting point 772'C, density 2.15g cm^-3) at 780'C. During electrolysis how would the metal occur?
A - solid on surface
B - liquid on surface
C - solid at bottom
D - liquid at bottom
A - not warm enough for solid to have melted and metal has lighter density that solution so would not sink
Which of the following chlorides is most likely to be soluable in tetrachloromethane, CCl4?
A - barium chloride
B - caesium chloride
C - calcium chloride
D - phosphorous chloride
D -
In which of the following liquids does hydrogen bonding occur?
A - ethanoic acid
B - ethyl ethanoate
C - hexane
D - hex-1-ene
A - alcohols contain O—H bond
A compound boils at -33’C. It also dissolves in water to give an alkaline solution.
Which type of bonding is present within compound?
A - metallic
B - covalent (polar)
C - ionic
D - covalent (non-polar)
B
Which of the following compounds has polar molecules?
A - CH4
B - CO2
C - NH3
D - CCl4
C - all other are symmetrical therefore non-polar
Which of the following has a covalent molecular structure?
A - radium chloride
B - a noble gas
C - silicon dioxide
D - a fullerene
D
