Neco 2020 Chemistry Question 22

Practice objective / multiple choice question 22 from the 2020 Neco Chemistry examination.

Neco 2020 Chemistry Objective / Multiple Choice Hard Difficulty
Question 22 NECO • 2020 • CHEMISTRY • objective

An alloy is reported to contain 70.0\% copper by mass. A 10.0 g sample of the alloy is melted and cast into a rectangular bar measuring 2.0 cm × 1.0 cm × 0.5 cm. The measured density of the bar is 8.70 g cm\( ^{-3} \). Given densities \( \rho_{\text{Cu}} = 8.96 \) g cm\( ^{-3} \) and \( \rho_{\text{Zn}} = 7.14 \) g cm\( ^{-3} \), (a) calculate the density expected for a 70\% Cu-30\% Zn alloy using the rule of mixtures, and (b) determine the actual mass percent of copper in the alloy based on the measured density.

Answer Options

A. Expected density ≈8.20 g cm⁻³; actual Cu mass percent ≈80 %
Correct Answer B. Expected density ≈8.32 g cm⁻³; actual Cu mass percent ≈88 %
C. Expected density ≈8.60 g cm⁻³; actual Cu mass percent ≈92 %
D. Expected density ≈8.45 g cm⁻³; actual Cu mass percent ≈85 %
Correct Answer
B
Correct Option:
Expected density ≈8.32 g cm⁻³; actual Cu mass percent ≈88 %

About This Question

This is Neco 2020 Chemistry Question 22. It is one of the objective questions from the 2020 Neco Chemistry examination.

Difficulty level: Hard .

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