Multiple Choice
A student performs a Benedict's test on a sample to detect the presence of reducing sugars. After heating, the solution changes from blue to brick-red. What does this result indicate?
23
views
4. BONUS: Lab Techniques and Procedures
Test for Ions and Gases
Struggling with General Chemistry?
Join thousands of students who trust us to help them ace their exams!Watch the first videoMultiple Choice
Which test is commonly used to identify the presence of carbon dioxide gas?
A
Place moist red litmus paper in the gas; it turns blue.
B
Add hydrochloric acid to the sample; effervescence occurs.
C
Bubble the gas through limewater; a milky white precipitate forms.
D
Expose the gas to a glowing splint; the splint relights.
Verified step by step guidance1
Understand that the problem asks for a common test to identify carbon dioxide (CO\_2) gas.
Recall that carbon dioxide is an acidic oxide and reacts with calcium hydroxide (limewater) to form calcium carbonate, which is insoluble and appears as a milky white precipitate.
Write the chemical reaction for the test: \(\mathrm{CO\_2 (g) + Ca(OH)\_2 (aq) \rightarrow CaCO\_3 (s) + H\_2O (l)}\).
Recognize that bubbling the gas through limewater and observing the formation of a milky white precipitate is a classic and reliable test for CO\_2.
Note that other options (moist red litmus turning blue, effervescence with HCl, glowing splint relighting) correspond to different gases or reactions and are not characteristic tests for CO\_2.
Related Videos
Related Practice
Test for Ions and Gases practice set
Problem sets built by lead tutorsExpert video explanations