Question 1

Which reagent is commonly used to test for the presence of chloride ions ($\mathrm{Cl^-}$) in a solution, and what is the expected observation?

Accepted Answer

Add silver nitrate ($\mathrm{AgNO_3}$); a white solid precipitate forms.

Question 2

A student adds silver nitrate ($\mathrm{AgNO_3}$) to a solution and observes a solid precipitate. Which anion could be present?

Accepted Answer

Bromide ion ($\mathrm{Br^-}$)

Question 3

When hydrochloric acid ($\mathrm{HCl}$) is added to a solution containing carbonate ions ($\mathrm{CO_3^{2-}}$), what is the expected observation and why?

Accepted Answer

Bubbles of gas are observed due to the formation of $\mathrm{CO_2}$.

Question 4

Which test would you use to distinguish between sulfate ($\mathrm{SO_4^{2-}}$) and sulfite ($\mathrm{SO_3^{2-}}$) ions in solution?

Accepted Answer

Add barium chloride ($\mathrm{BaCl_2}$); sulfate forms a white precipitate, sulfite does not.

Question 5

A solution is tested with silver nitrate ($\mathrm{AgNO_3}$) after acidifying with nitric acid ($\mathrm{HNO_3}$), and a yellow solid precipitate forms. Which anion is most likely present?

Accepted Answer

Iodide ion ($\mathrm{I^-}$)

Question 6

Which observation would confirm the presence of carbonate ($\mathrm{CO_3^{2-}}$) or bicarbonate ($\mathrm{HCO_3^-}$) ions in an unknown solution?

Accepted Answer

Effervescence (bubbling) upon addition of hydrochloric acid ($\mathrm{HCl}$)

Question 7

A laboratory technician adds barium chloride ($\mathrm{BaCl_2}$) to a solution after acidifying it with hydrochloric acid ($\mathrm{HCl}$). A white precipitate forms. Which anion is most likely present?

Accepted Answer

Sulfate ion ($\mathrm{SO_4^{2-}}$)

Question 8

Which of the following anions does NOT form a solid precipitate when tested with silver nitrate ($\mathrm{AgNO_3}$) after acidification with nitric acid ($\mathrm{HNO_3}$)?

Accepted Answer

Nitrate ion ($\mathrm{NO_3^-}$)

Question 9

A solution is suspected to contain sulfite ions ($\mathrm{SO_3^{2-}}$). Which test and observation would confirm their presence?

Accepted Answer

Add hydrochloric acid ($\mathrm{HCl}$); observe a solid in the aqueous layer.

Question 10

Which sequence of reagents would you use to confirm the presence of nitrate ions ($\mathrm{NO_3^-}$) in a solution?

Accepted Answer

Add cold iron(II) sulfate ($\mathrm{FeSO_4}$), then carefully add concentrated sulfuric acid ($\mathrm{H_2SO_4}$) to form a brown ring.

Question 11

A patient’s urine sample is tested for the presence of sulfate ions ($\mathrm{SO_4^{2-}}$) as part of a diagnostic procedure. Which result would indicate a positive test?

Accepted Answer

A white precipitate forms after adding barium chloride ($\mathrm{BaCl_2}$) and hydrochloric acid ($\mathrm{HCl}$).

Question 12

Which of the following best explains why nitric acid ($\mathrm{HNO_3}$) is added before silver nitrate ($\mathrm{AgNO_3}$) in the test for halide ions?

Accepted Answer

To remove interfering ions such as carbonate and sulfite that could also form precipitates with silver ions.

Question 13

A solution gives a solid precipitate when tested with both silver nitrate ($\mathrm{AgNO_3}$) and barium chloride ($\mathrm{BaCl_2}$) after acidification. Which anion could be responsible for both observations?

Accepted Answer

Carbonate ion ($\mathrm{CO_3^{2-}}$)

Question 14

In a forensic investigation, a white solid is found at a crime scene. When dissolved in water and tested with silver nitrate ($\mathrm{AgNO_3}$) after acidification, a white precipitate forms. Which further test could help distinguish between chloride, bromide, and iodide ions?

Accepted Answer

Observe the color of the precipitate and test its solubility in ammonia solution.

Question 15

A student is given an unknown solution. After adding hydrochloric acid ($\mathrm{HCl}$), a gas is evolved that turns limewater milky. Which ion is most likely present?

Accepted Answer

Carbonate ion ($\mathrm{CO_3^{2-}}$)

Question 16

Which of the following best describes the observation when a solution containing iodide ions ($\mathrm{I^-}$) is tested with silver nitrate ($\mathrm{AgNO_3}$) after acidification?

Accepted Answer

A yellow solid precipitate forms.

Identification of Common Anions in Aqueous Solution: Tests and Observations

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