# How to Solve Chemical Calculation involving Acid and Alkali| Step-by-Step Explanation| 2018/P1/Q11 [Online Video]

## Question

Sodium hydroxide reacts with sulfuric acid. The equation for the reaction is shown.
2NaOH + H2SO4 → Na2SO4 + 2H2O
Which volume of 0.20 mol/dm3 sodium hydroxide reacts completely with a solution containing 0.49 g of sulfuric acid? [Mr: H2SO4, 98]
A) 12.5 cm3 B) 25.0 cm3 C) 50.0 cm3 D) 100.0 cm3

## Type of chemical reaction

The chemical reaction that we are dealing with in this question is a neutralisation reaction. Reaction between an acid and an alkali will produce salt and water. In this question, the alkali is sodium hydroxide, while the acid is sulfuric acid. Both react to form sodium sulfate salt and water.

## Mole Calculation

Chemical substances in the chemical equation are balanced by moles. Hence, we definitely need to know different ways to determine number of moles. Check out this link for details.

From the balanced equation, we know that 2 moles of sodium hydroxide reacts with 1 mole of sulfuric acid.  We need to start off by determining the number of moles of sulfuric acid, as we have its mass and relative molecular mass, which has the same value as molar mass. Then, we will determine the number of moles of sodium hydroxide by comparing mole ratio. We will then be able to achieve the volume of sodium hydroxide.

## Unit conversion

In this video, I will also go through with you a very important skill – unit conversion. We will focus on that for mass and volume.
For mass, we will investigate how to convert units from ton to kg to g and vice versa.
For volume, we will investigate how to convert units from m3 to dm3 to cm3 and vice versa.

GCE O level, Singapore, 2018/P1/11

Topic: Mole and Balancing of Chemical Equations, O Level Chemistry, Singapore