Why do you test with dil HCl before conc H2SO4?

There are some ions like, SO2-3,S2-,NO-2 andCH3COO- which can react with dilute/conc. Now if conc. H2SO4 is used first then the anions of both the types will react. Hence, it is desired to test acid radicals first with dilute H2SO4 and then with conc.

Why do we add dil HCl before proceeding to Analyse cations of Group II?

dilute HCl increasing the concentration of h + ions in the solution and hence suppresses the dissociation of H2S due to common Ion effect. As a result of which the sulphide ions concentration is sufficient only to exceeds the solubility product of the sulphides of Group II cations.

Why is dilute acid used in an experiment?

Using concentrated acids and diluting them down as required helps to save space in the lab and gives you the flexibility to make up any concentration you need. The drawback is that working with concentrated acids can be very hazardous.

Why should dilute hydrochloric acid not be used instead of nitric acid?

As you said, one cannot add HCl to destroy carbonates in a sample which is to be tested for halide ions. Dilute nitric is the only choice, because you would not use sulfuric acid in the case of halides because (i) your test sample may contain ions which will precipitate with sulfate (Ba, Ag, Pb, Ca etc.).

Can we use dil HCl instead of Dil H2SO4?

HCl and HNO3 are not used in the titration of Mohr’s salt in place of sulfuric acid because: As dilute sulfuric acid is ideal for redox titration because it is neither an oxidizing agent and nor a reducing agent.

Why do we use H2SO4 instead of HNO3 or HCl in salt analysis?

When HCl dissolve in water, it will dissociate into one mole of H+ ion and Cl- ions. Whereas, the H2SO4 dissociate into two mole of 2H+ and SO4^2- . Hence,the number of H+ ions produced by H2SO4 is higher and easily replace with other compounds. It is possible for these acids to form more than one type of salt.

Why do we add HCl before h2s?

The concentration of sulphide ions is suppressed by HCl due to common ion effect. The already present H+ ions suppress the dissociation of H2S by moving the reaction in the backward reaction. Hence a lesser no of sulphide ions is produced so that only those cations are precipitated having lower solubility product.

Why should the solution be concentrated before proceeding to Group V?

Before proceeding to group 5, the solution is made concentrated by adding excess of NH4Cl to ensure that the ionic product of group 6 cation that is Mg+2 does not exceed its solubility product, and hence it is not precipitated along with group 5 cations.

When diluting an acid always pour the?

Mixing liquids: When mixing concentrated (>10\%) aqueous chemicals (such as acids, bases and oxidizers), always pour the more concentrated solution into the less concentrated one to avoid splattering. This common rule has two convenient mnemonics: 1) (AAA) Always Add Acid to water.

Why do we add nitric acid to test for anions?

The nitric acid is added first to remove any carbonate ions that might be present – they would produce a white precipitate of silver carbonate, giving a false positive result for chloride ions.

Why would dilute hydrochloric acid not be used to acidify the reaction?

An unknown amount of the potassium manganate(VII) would be used in side reactions, and so the titration result would be inaccurate. This is why you don’t acidify the solution with hydrochloric acid.

What is the difference between dilute HCl and concentrated H2SO4?

In quantitative test, dilute HCl is weaker acid so it will not react with all anions. But concentrated H2SO4 is a strong acid that reacts with all acids. In a certain circumstances, sulphuric acid can function as an oxidising agent, resulting in production of different substances

Why does dilute HCl not react with all anions?

Luckily, there are simple steps you can take to dramatically reduce Google’s tracking. But(Continue reading) In quantitative test, dilute HCl is weaker acid so it will not react with all anions. But concentrated H2SO4 is a strong acid that reacts with all acids.

Why is hydrochloric acid used to test for sulfate ions?

Explain why, in a test for sulfate ions, the sample is acidified with hydrochloric acid first. Carbonate ions also produce a white precipitate with barium chloride solution. The acid reacts with any carbonate ions present. This removes them, so stopping them giving a false positive result.

Why can’t dilute hydrochloric acid be used to acidify carbonate ions?

Carbonate ions also produce a white precipitate with silver nitrate solution. The acid reacts with any carbonate ions present. This removes them, so stopping them giving an incorrect positive result for chloride ions. Explain why, in a test for halide ions, dilute hydrochloric acid cannot be used to acidify the sample.