Each student in Ms. Major's class was given an unknown substance. Ms. Major gave her students a list, shown below, of substances and their properties to help them identify their unknown.

Question

Substance Density Boiling Point Appearance
Water 1.0 g/mL 100°C colorless liquid
Ethanol 0.789 g/mL 78.4°C colorless liquid
Sodium Hydroxide 2.13 g/mL 1388°C white solid
Phosphoric Acid 1.685 g/mL 158°C white solid or colorless liquid

If a student's unknown is a white solid and its density was calculated to be about 1.7 g/mL, it is most likely _______.
A.
water
B.
ethanol
C.
sodium hydroxide
D.
phosphoric acid

Answer 1

If the student's unknown substance is a white solid with a density of about 1.7 g/mL, it is most likely D. phosphoric acid.

Here's the reasoning:

• Water is a colorless liquid with a density of 1.0 g/mL.
• Ethanol is also a colorless liquid with a density of 0.789 g/mL.
• Sodium hydroxide is a white solid but has a much higher density of 2.13 g/mL.
• Phosphoric acid can be a white solid or a colorless liquid and has a density of 1.685 g/mL, which is closest to the student's calculated density of about 1.7 g/mL.

Therefore, given the properties, the answer is D. phosphoric acid.