I need help on this one too I think it might be (b)
The question requires us to draw the structural formula, provide the name and highlight any functional groups for the compound: diethyl ether.
The molecule diethyl ether can be represented as it follows, with two ethyl groups (-CH2CH3) bonded to a oxygen atom:
Note that the functional group ether (R-O-R) is present in the structre and highlighted in blue in the image. The official name of diethyl ether is ethoxyethane.
Answer : The number of moles in 369 grams of calcium hydroxide is, 4.98 moles
Explanation : Given,
Mass of calcium hydroxide = 369 g
Molar mass of calcium hydroxide = 74.093 g/mole
Formula used :

Now put all the given values in this formula, we get the moles of calcium hydroxide.

Therefore, the number of moles in 369 grams of calcium hydroxide is, 4.98 moles
For #4 first find the molar mass(M) of copper then use that and the mass (m) n=m/M to find moles(n) using moles and the volumes find the concentration using c=n/V