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.
The answer is (2) KNO3. This depends on the solubility of these four compounds at 10℃. For NaCl, it is 35.8 g, For NaNO3, 80.8 g. KCl, 31.2 g. KNO3, 21.9g. So only KNO3 is less than 25.0 g.
2.91 mol Al * ( 26.982 g Al / 1 mol Al) = 78.518 grams