What are the molality and mole fraction of solute in a 35.9 percent by mass aqueous solution of formic acid (hcooh)?

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1- The molarity of HCOOH = 9.515 M.

2- The mole fraction of HCOOH = 0.18.

Explanation:

1- The molarity of HCOOH:

We can calculate the molarity of HCOOH using the relation:

M = (10pd)/molar mass.

p is the percent by mass of HCOOH = 35.9 %.

d is the specific gravity of HCOOH = 1.22 g/cm³.

Molar mass of HCOOH = 46.03 g/mol.

∴ M = (10pd)/molar mass = (10)(35.9 %)(1.22 gcm³) / (46.03 g/mol) = 9.515 M.

2- The mole fraction of HCOOH:

We can suppose that we have a 100 g solution, that contains 35.9 g of HCOOH and 64.1 g of water.

The mole fraction of HCOOH = (no. of moles of HCOOH) / (no. of moles of HCOOH + no, of moles of water).

no. of moles of HCOOH = mass / molar mass = (35.9 g)/(46.03 g/mol) = 0.78 mol.

no. of moles of water = mass / molar mass = (64.1 g)/(18.0 g/mol) = 3.56 mol.

The mole fraction of HCOOH = (no. of moles of HCOOH) / (no. of moles of HCOOH + no, of moles of water) = (0.78 mol) / (0.78 mol + 3.56 mol) = 0.18.

A) litmus is red

Explanation:

To answer this question, it can be helpful to have the color charts. Litmus, phenolphthalein and methyl orange are ways to test the pH of a substance.

Litmus paper

Litmus can tell you if a substance is an acid or a base. You need to put the substance on both red litmus and blue litmus paper.

pH < 7: both papers are red. 3.0 is less than 7.

pH = 7: none of them change color

pH > 7: both papers are blue

Phenolphthalein

When this indicator is added to a substance, the result is either colorless or pink.

0 < pH ≤ 7: colorless. The color is not red or blue for pH 3.0.

pH > 7: pink

Methyl orange

0 < pH < 4: red. The color is not yellow if the pH is 3.0.

4 ≤ pH < 5: orange

pH ≥ 5: yellow