Which of the following molecules has a geometry described as trigonal planar? A) CHF3 B) BF3 D) OF2 30) E) SiH4 C) PF3 31) After drawing the Lewis dot structure for SBr2, determine the number of single bonds, 31) double bonds, and lone pairs on the central atom.A) 2,0,2 B) 2, 0,1 C) 2,0,0 32) Which of the following compounds is a strong electrolyte? A) H20 B) CH40 C) NaF D) 0, 2,0 E) 1,1,0 32) D) CH4 E) 02 33) 33) Identify the major ionic species present in an aqueous solution of Na2CO3. A) Naz, C2, 03 B) Na+, CO32- C) Naz, CO32 D) Na, C, 02- E) Nat, 04, 032- 34) What mass of C6H1206 (glucose) is needed to prepare 450. ml. of a 0.650 M solution 34) of glucose in water? A) 293 g B) 0.692 g C) 52.7 g D) 0.293 g E) 125 g 35) What mass of K2CO3 is needed to prepare 200. mL of a solution having a potassium 35) ion concentration of 0.150 M A) 4.15 g B) 1.49 g C) 13.8 g D) 2.07 g E) 10.4 g 36) A solution is prepared by dissolving 2 g of KCl in 100 g of H2O. In this solution. H2O 36) is the A) solution B) ionic compound C) solute D) solid El solvent 37) What is the molarity of a solution that contains 5.0 moles of solute in 2.00 liters of solution? A) 2.5 B) 1.5 C) 3.5 D) None of the above E14.4
The Correct Answer and Explanation is :
Solutions to the Questions:
1. Which molecule has a trigonal planar geometry?
Answer: B) BF₃
Explanation:
The geometry of a molecule depends on its central atom and the surrounding atoms. Boron trifluoride (BF₃) has a central boron atom surrounded by three fluorine atoms. Boron has three valence electrons and forms three single bonds with fluorine, leaving no lone pairs on boron. According to VSEPR theory, the molecule adopts a trigonal planar geometry to minimize electron pair repulsion, with bond angles of 120°.
Other molecules:
- CHF₃: Tetrahedral geometry due to four regions of electron density.
- OF₂: Bent geometry due to two lone pairs on oxygen.
- SiH₄: Tetrahedral geometry.
- PF₃: Trigonal pyramidal due to one lone pair on phosphorus.
2. Lewis structure for SBr₂: How many single bonds, double bonds, and lone pairs on sulfur?
Answer: A) 2 single bonds, 0 double bonds, 2 lone pairs
Explanation:
Sulfur is the central atom in SBr₂. It forms two single bonds with two bromine atoms. Sulfur has six valence electrons, so after bonding with bromine (which contributes two electrons), four electrons remain as two lone pairs on sulfur. There are no double bonds.
3. Which compound is a strong electrolyte?
Answer: C) NaF
Explanation:
A strong electrolyte dissociates completely into ions in water. Sodium fluoride (NaF) is an ionic compound and dissociates into Na⁺ and F⁻ in water, making it a strong electrolyte. Water (H₂O) and methanol (CH₄O) are covalent and do not dissociate significantly, while O₂ and CH₄ are non-electrolytes.
4. Major ionic species in an aqueous solution of Na₂CO₃?
Answer: B) Na⁺, CO₃²⁻
Explanation:
Sodium carbonate (Na₂CO₃) dissociates completely in water into two sodium ions (Na⁺) and one carbonate ion (CO₃²⁻).
5. Mass of glucose to prepare 450 mL of 0.650 M solution?
Answer: C) 52.7 g
Explanation:
Moles of glucose = ( M \times V = 0.650 \times 0.450 = 0.2925 \, \text{mol} )
Molar mass of glucose (C₆H₁₂O₆) = 180 g/mol
Mass = ( 0.2925 \, \text{mol} \times 180 \, \text{g/mol} = 52.7 \, \text{g} )
6. Mass of K₂CO₃ to prepare 200 mL solution with 0.150 M K⁺ concentration?
Answer: A) 4.15 g
Explanation:
For K⁺ concentration of 0.150 M, K₂CO₃ concentration is ( \frac{0.150}{2} = 0.075 \, \text{M} ).
Moles of K₂CO₃ = ( 0.075 \times 0.200 = 0.015 \, \text{mol} )
Molar mass of K₂CO₃ = 138 g/mol
Mass = ( 0.015 \, \text{mol} \times 138 \, \text{g/mol} = 4.15 \, \text{g} )
7. In the KCl solution, what is H₂O?
Answer: E) Solvent
Explanation:
The solvent is the substance in which the solute dissolves. In this case, water (H₂O) is the solvent, and KCl is the solute.
8. Molarity of solution with 5.0 moles of solute in 2.00 liters?
Answer: A) 2.5 M
Explanation:
Molarity = ( \frac{\text{Moles of solute}}{\text{Volume of solution in liters}} )
Molarity = ( \frac{5.0}{2.00} = 2.5 \, \text{M} ).