Which of the following compounds would be found as mostly molecules when placed into water? 
I. Be(OH)₂                     II. HNO₃                        III. LiOH                        IV. (CH­₃)₂NH                 V. CaO
a) I, IV, V
b) I only
c) I and IV
d) IV only
e) None of the above

• A. I, IV, V
• B. I only
• C. I and IV
• D. IV only
• E. None of the above

Answer: (C)

Verified step by step guidance

1. Step 1: Understand the concept of dissociation in water. When ionic compounds are placed in water, they tend to dissociate into ions, whereas covalent compounds may remain as molecules.
2. Step 2: Analyze each compound to determine if it is ionic or covalent. Ionic compounds typically dissociate into ions in water, while covalent compounds may remain as molecules.
3. Step 3: Consider Be(OH)2. Beryllium hydroxide is a weak base and does not dissociate completely in water, so it may remain mostly as molecules.
4. Step 4: Consider (CH3)2NH. Dimethylamine is a covalent compound and a weak base, which means it does not dissociate completely in water, so it may remain mostly as molecules.
5. Step 5: Compare the dissociation behavior of the other compounds (HNO3, LiOH, CaO) in water. Strong acids like HNO3 and strong bases like LiOH typically dissociate completely into ions, while CaO reacts with water to form Ca(OH)2, which dissociates into ions.