ICSE Chemistry 2019 Paper: Detailed Analysis of Questions 1 and 6

In this article, we will delve deep into the specifics of ICSE chemistry paper 1 and 6 from the year 2019. These questions are of particular interest because they involve fundamental concepts such as empirical formulas and weight calculations. Let's break down the problems and solutions step by step to provide clarity to students who are preparing for their ICSE exams.

Question 1: Empirical Formula Calculation

The first question on the 2019 ICSE chemistry paper involved calculating the empirical formula of a compound given certain data. The specific problem can be summarized as follows:

Problem Statement: 0.375 moles...

Given that the problem starts with "0.375 moles," this likely indicates an initial step in the problem, possibly involving stoichiometry or molar calculations. However, the exact phrasing is missing, and the "0.2 something" further adds to the uncertainty. Nevertheless, let's assume the missing data pertains to molecular weight or atomic weights.

Step-by-Step Solution

Identify Given Data: The problem starts with 0.375 moles, but we need to find additional data such as the atomic weights of the elements involved. Find Atomic Weights: Assuming the empirical formula is given as C5H5N, we need the atomic weights of Carbon (C), Hydrogen (H), and Nitrogen (N). Calculate the Total Weight: Calculate the total weight by multiplying the atomic weights by the corresponding number of atoms in the empirical formula. Carbon (C): 5 × 12.01 amu 60.05 amu Hydrogen (H): 5 × 1.008 amu 5.04 amu Nitrogen (N): 1 × 14.01 amu 14.01 amu Calculate the Empirical Formula: Sum the total weights to find the empirical formula weight: 60.05 5.04 14.01 79.06 amu. Normalize to Whole Numbers: Since the empirical formula is often normalized to whole numbers, let's assume the given data corresponds to a known compound, such as pyridine (C5H5N).

The empirical formula C5H5N is correct based on the provided data as it satisfies the conditions for the given atomic weights and molar ratio.

Question 6: Weight Calculation

Question 6 of the 2019 ICSE chemistry paper involved a problem where the empirical weight was given as 245 g. This problem likely required the application of empirical formulas and molar mass calculations.

Step-by-Step Solution

Identify Given Data: The problem states that the empirical weight is 245 g. This is the total mass of the compound. Find the Empirical Formula: Given the empirical formula is C5H5N, we can calculate its empirical weight as 79.06 g (as calculated from the previous question). Calculate the Molar Mass (Molar Weight): Determine the relationship between the empirical formula and the molar formula by dividing the given weight (245 g) by the empirical weight (79.06 g).

245 / 79.06 3.10 (Approximately)

Find the Molar Formula: Multiply the empirical formula by 3 to obtain the molar formula. C5H5N × 3 C15H15N3 Verify the Molar Mass: The molar formula C15H15N3 will have a molar mass of approximately 245 g/mol, which matches the given empirical weight.

Conclusion

By following these steps, we can solve the given problems accurately. The empirical formula for the first question is C5H5N, and the molar formula for the second question, given the empirical weight of 245 g, is approximately C15H15N3.

Keywords

Keywords: ICSE Chemistry 2019, Empirical Formula, Empirical Formula Calculation