Chemistry Answers

If Mg and HNO₃ undergo a single-displacement reaction, what balanced equation shows the products formed?

• Mg + HNO₃ → H₂ + Mg(NO₃)₂
• Mg + 2HNO₃ → H₂ + Mg(NO₃)₂
• 2Mg + 2(HNO₃) → 2MgH + 2(NO₃)
• Mg + 2HNO₃ → MgH + (NO₃)

it's NOT: Mg + HNO₃ → H₂ + Mg(NO₃)₂

Refer to the two formulas for glucose.

Formula A: C₁₁H₂₂O₁₁

Formula B: CH₂O

What is difference between the two formulas?

• Formula A is the structural formula for glucose because it shows the arrangement of atoms in the compound.  Formula B is the empirical formula for glucose because it shows the smallest whole-number ratio for the different atoms in the compound.

• Formula A is the molecular formula for glucose because it shows the arrangement of atoms in the compound.  Formula B is the structural formula for glucose because it shows the smallest whole-number ratio for the different atoms in the compound.

• Formula A is the molecular formula for glucose because it shows the actual number of atoms in the compound.  Formula B is the empirical formula for glucose because it shows the smallest whole-number ratio for the different atoms in the compound/

A welding fuel gas contains carbon and hydrogen only. Burning a small sample of it in oxygen gives 3.38 g carbon dioxide, 0.690 g of water and no other products. A volume of 10.0 L (measured at S.T.P.) of this welding gas is found to weigh 11.6 g. Calculate (i) empirical formula, (ii) molar mass of the gas, and (iii) molecular formula.

Ethane (C₂H₆) has one C-C bond and six C-H bonds. The electronegativity difference between carbon and hydrogen is less than 0.4.

What is a property of ethane?

• Ethane is nonpolar because it has an even distribution of charge across the entire molecule, which results from the large electronegativity difference between the carbon and hydrogen atoms.
• Ethane is nonpolar because it has an even distribution of charge across the entire molecule, which results from the small electronegativity difference between the carbon and hydrogen atoms. 
• Ethane is nonpolar because it has an uneven distribution of charge across the entire molecule, which results from the small electronegativity difference between the carbon and hydrogen atoms.
• Ethane is nonpolar because it has an uneven distribution of charge across the entire molecule, which results from the large electronegativity difference between the carbon and hydrogen atoms.

it's NOT: the bolded option (bullet point #1)

What is the molecular geometry of a molecule made of two atoms that share one pair of electrons and have no lone electrons pairs?

• trigonal planar
• bent
• linear
• trigonal pyramidal

it's NOT: trigonal planar

Which statement describes a space-filling model of a molecule?

• The radii of the atoms are represented by the symbol of the atom surrounded by dots in the space-filling model.
• The radii of the “ball” that is attached to a “stick” in the space-filling model is equal to the radii of the atoms they represent.
• The radii of the spheres in a space-filling model are proportional in size to the radii of the atoms they represent.
• The radii of the atoms present in the compound determine the length of the bonds in a space-filling model.

it's NOT: The radii of the atoms present in the compound determine the length of the bonds in a space-filling model.

Why are noble gases, like helium and krypton, unlikely to form a bond?

• They have full valence orbitals and already have low energy.
• They always have an equal number of protons and electrons.
• They are nonmetals and gases and therefore their ionization energy is too high to form a bond.
• They do not have valence electrons and therefore cannot form bonds by sharing or trading electrons.

its NOT: They are nonmetals and gases and therefore their ionization energy is too high to form a bond.

Two hydrogen atoms covalently bond to form a hydrogen molecule.

What is true about the hydrogen molecule?

• The hydrogen molecule has less energy than the two atoms.
• The hydrogen molecule has more energy than the two atoms.
• The hydrogen molecule has the same energy as the two atoms.
• The hydrogen molecule can have more or less energy than the hydrogen atoms.

it is NOT: The hydrogen molecule has more energy than the two atoms.

If a crystal lattice structure is so hard, what causes most ionic compounds to be brittle?

• Applying force, such as striking the crystal with a hammer, can shift one layer of ions, causing ions of different charges to align, repel each other, and fragment the crystal.
• Applying force, such as striking the crystal with a hammer, can release protons, causing ions of similar charges to align, repel each other, and dissolve the crystal.
• Applying force, such as striking the crystal with a hammer, can release electrons, causing ions to alter their charges, repel each other, and dissolve the crystal.
• Applying force, such as striking the crystal with a hammer, can shift ions, causing ions of similar charges to align, repel each other, and fragment the crystal.

(which of the answer is correct)

• it is not: Applying force, such as striking the crystal with a hammer, can release electrons, causing ions to alter their charges, repel each other, and dissolve the crystal.

What is true about ionic compounds?

Select all that apply.

• Electrons are not free to move.
• Properties of the compound are different than the properties of individual atoms that make the compound.
• Electrons are not involved in the formation of an ionic bond, since ions do not have valence electrons.
• They may have a positive or negative charge.

(more than one correct answer)