Correct Answer: A) Silicon
Explanation: Silicon is widely used in the production of computer chips and solar cells due to its excellent semiconductor properties.
A) Linear
B) Tetrahedral
C) Bent
D) Trigonal planar
Correct Answer: C) Bent
Explanation: Water has a bent molecular shape due to the two lone pairs of electrons on the oxygen atom, which repel the bonding pairs, creating a bent shape.
A) Silicon
B) Germanium
C) Gallium
D) Selenium
Correct Answer: A) Silicon
Explanation: Silicon is widely used in the production of computer chips and solar cells due to its excellent semiconductor properties.
A) Good conductivity of heat and electricity
B) High ionization energies
C) Low electronegativity
D) High thermal conductivity
Correct Answer: B) High ionization energies
Explanation: Nonmetals are characterized by high ionization energies, meaning they do not easily lose electrons. This property makes them poor conductors of heat and electricity.
A) Methane
B) Ammonia
C) Ethanol
D) Acetic acid
Correct Answer: B) Ammonia
Explanation: The Haber process synthesizes ammonia from nitrogen and hydrogen gases, using an iron catalyst under high pressure and temperature. This process is critical for producing fertilizers.
A) -1
B) -2
C) 0
D) +1
Correct Answer: A) -1
Explanation: In hydrogen peroxide (H₂O₂), oxygen has an unusual oxidation number of -1, compared to its usual oxidation number of -2 in most other compounds.
A) Saltwater
B) Air
C) Steel
D) Sand and iron filings
Correct Answer: D) Sand and iron filings
Explanation: Sand and iron filings form a heterogeneous mixture because the two substances can be easily distinguished and are not uniform throughout.
A) Redox potential
B) Hydrogen ion concentration
C) Thermal conductivity
D) Molecular weight
Correct Answer: B) Hydrogen ion concentration
Explanation: The pH scale measures the hydrogen ion concentration in a solution, indicating its acidity or basicity. A pH of 7 is neutral, below 7 is acidic, and above 7 is basic.
A) Charles’s Law
B) Boyle’s Law
C) Avogadro’s Law
D) Dalton’s Law
Correct Answer: A) Charles’s Law
Explanation: Charles’s Law states that the volume of an ideal gas is directly proportional to its absolute temperature at constant pressure.
A) Amorphous solid
B) Polymeric solid
C) Crystalline solid
D) Composite solid
Correct Answer: C) Crystalline solid
Explanation: Crystalline solids have a highly ordered atomic structure, typically formed when liquid metals solidify, creating a periodic and repeating pattern.
A) Increases it
B) Decreases it
C) Does not change it
D) Eliminates it
Correct Answer: B) Decreases it
Explanation: A catalyst lowers the activation energy of a chemical reaction, thereby increasing the reaction rate without being consumed in the process.
A) Boron
B) Magnesium
C) Lead
D) Mercury
Correct Answer: A) Boron
Explanation: Boron is classified as a metalloid because it exhibits properties intermediate between metals and nonmetals. It is used in glass production and as a semiconductor.
A) Iron
B) Aluminum
C) Titanium
D) Copper
Correct Answer: C) Titanium
Explanation: The Kroll process is an industrial method for the production of titanium, involving the reduction of titanium tetrachloride with magnesium.
A) London dispersion forces
B) Dipole-dipole interactions
C) Hydrogen bonding
D) Ionic bonding
Correct Answer: C) Hydrogen bonding
Explanation: Hydrogen bonding, a strong type of dipole-dipole interaction, occurs between the hydrogen of one water molecule and the oxygen of another. This interaction is responsible for many of water’s unique properties, including its relatively high boiling point compared to other molecules of similar size.
A) 18.01 g/mol
B) 28.01 g/mol
C) 32.00 g/mol
D) 44.01 g/mol
Correct Answer: D) 44.01 g/mol
Explanation: The molar mass of carbon dioxide is 44.01 g/mol, calculated by adding the molar masses of one carbon atom (12.01 g/mol) and two oxygen atoms (2 × 16.00 g/mol).
A) Sodium chloride (NaCl)
B) Water (H₂O)
C) Both A and B
D) Hydrogen gas (H₂)
Correct Answer: C) Both A and B
Explanation: The neutralization reaction between HCl and NaOH produces sodium chloride (NaCl) and water (H₂O), typical of an acid-base reaction.
A) Magnesium
B) Iron
C) Zinc
D) Copper
Correct Answer: A) Magnesium
Explanation: Magnesium is a central element in the chlorophyll molecule and is essential for photosynthesis in plants, allowing them to absorb energy from light.
A) Carbon dioxide
B) Sulfur dioxide
C) Methane
D) Nitrogen
Correct Answer: B) Sulfur dioxide
Explanation: Sulfur dioxide (SO₂) and nitrogen oxides are the primary gases responsible for the formation of acid rain. They react with water vapor in the atmosphere to form sulfuric and nitric acids, which fall as acid rain.
A) Sodium bicarbonate
B) Sodium chloride
C) Acetic acid
D) Methanol
Correct Answer: A) Sodium bicarbonate
Explanation: Sodium bicarbonate (baking soda) is commonly used as an antacid to neutralize stomach acid and relieve heartburn, indigestion, and upset stomach.
A) Moles of solute per liter of solvent
B) Moles of solute per kilogram of solvent
C) Moles of solute per liter of solution
D) Grams of solute per liter of solution
Correct Answer: C) Moles of solute per liter of solution
Explanation: Molarity is calculated as the moles of solute divided by the liters of solution. It measures the concentration of a solution and is expressed in moles per liter (M).
A) Hydrogen
B) Carbon
C) Oxygen
D) Sodium
Correct Answer: D) Sodium
Explanation: Sodium is defined by having 11 protons in its nucleus. It’s a soft, highly reactive metal and a key component of table salt.
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