STUDENT SPACE · TOPIC 4

Concentration and titration calculations

Convert concentration units and calculate unknown concentration from titration data.

The essentials

Try each question before opening its hint or answer. Use paper for calculations and diagrams.

Why does the expression 0.100 × 20.0 give the wrong number of moles for 20.0 cm³ solution?

Need a hint for Question 1?

Use the relationships above and check particle ratios and units.

Check Question 1

The volume must be in dm³: use 0.0200, not 20.0.

4.0 g NaOH is made up to 250 cm³ solution. Find concentration in g/dm³ and mol/dm³. M = 40 g/mol.

Need a hint for Question 2?

Convert 250 cm³ to dm³; use mass or moles per volume.

Check Question 2

4.0/0.250 = 16 g/dm³; (4.0/40)/0.250 = 0.40 mol/dm³.

HCl + NaOH → NaCl + H₂O. Find the volume of 0.100 mol/dm³ NaOH needed for 25.0 cm³ of 0.200 mol/dm³ HCl.

Need a hint for Question 3?

Find acid moles, use the 1:1 ratio and then calculate alkali volume.

Check Question 3

n(HCl) = 0.200 × 0.0250 = 0.00500 mol. V(NaOH) = 0.0500 dm³ = 50.0 cm³.

Use Lesson 4 in your worksheet for written practice. Your teacher will discuss those answers in class.