Oquizy

They test soil samples for acidity. Xinyi suggests adding calcium carbonate, but John worries about gas release affecting nearby experiments. Which gas is he worried about and why?

Ammonia, from nitrogenous compounds Carbon dioxide, from reaction with soil acids Hydrogen, from reaction with water in soil Oxygen, from decomposition of carbonate

Xinyi warms a mixture of ammonium chloride and sodium hydroxide. Damp red litmus paper held near the mouth of the test tube turns blue. What type of reaction occurred?

Acid-base reaction releasing ammonia Displacement reaction Neutralisation without gas release Thermal decomposition

After all the experiments, John jokingly says: 'If we add more water to this acid, it'll become weaker and less dangerous!' Which is the most accurate correction Xinyi should give?

Adding water removes hydrogen ions, making it less acidic. Diluting decreases concentration, but the acid remains strong if it fully ionises. He's right. Dilution turns strong acids into weak acids. The acid becomes neutral after enough dilution.

John adds excess zinc granules to 20 cm³ of dilute sulphuric acid and notices bubbles forming. Which of the following would increase the rate of reaction?

Add sodium chloride Dilute the acid further Use cold acid instead Use powdered zinc

Xinyi is doing a titration using sodium hydroxide and hydrochloric acid. Which indicator is most suitable, and what colour change is expected?

Litmus; blue to red Methyl orange; red to yellow Phenolphthalein; pink to colourless Universal indicator; green to blue

A farmer treats acidic soil with calcium hydroxide. What is the purpose of this treatment?

To add nitrogen To increase water content To make the soil more acidic To neutralise soil acidity

Xinyi studies industrial applications of sulfuric acid. Which of the following is a use of sulfuric acid?

As a fuel for combustion As a preservative in food In making detergents and fertilisers To soften hard water

Benedict added sodium hydroxide to ammonium chloride and warmed the mixture. What test confirms ammonia gas is released?

Add acid — bubbles form Bubble gas through limewater — it turns milky Use glowing splint — it relights Use red litmus paper — it turns blue

During a heated debate, John asks Xinyi why high pressure is used in the Haber process. Which of the following best explains the choice of 250 atm?

High pressure reduces the need for a catalyst Higher pressure shifts equilibrium towards ammonia, and 250 atm balances yield with operating cost Lower pressure speeds up the forward reaction The reaction is exothermic, so high pressure keeps the reactor cool

At the farm, John spots an experiment where ammonium chloride is being heated with sodium hydroxide. What is the observation that confirms ammonia production?

A colorless gas with pungent smell evolves A white precipitate forms Effervescence observed Temperature of the mixture decreases suddenly

Xinyi sets a mini-challenge: Which statement correctly explains why iron is used as a catalyst in the Haber process?

It allows the reaction to happen at room temperature It increases the rate of reaction without affecting equilibrium It increases the yield by shifting equilibrium It reduces the activation energy and shifts equilibrium to the right

John wants to prepare copper(II) sulfate crystals using an insoluble base. Which steps should he follow?

Add excess copper(II) oxide to warm sulfuric acid, filter, then crystallise the filtrate Mix copper(II) sulfate with sodium chloride and evaporate React copper(II) oxide with sodium hydroxide, then crystallise Titrate copper(II) oxide with sulfuric acid directly

Xinyi tries to prepare sodium sulfate by mixing sulfuric acid with sodium hydroxide. What technique should she use for the most accurate result?

Direct crystallisation Filtration Precipitation Titration

Which of the following salts is *not* commonly prepared by the titration method?

Ammonium sulfate Copper(II) sulfate Potassium nitrate Sodium chloride

Which of the following statements about solubility is true?

All carbonates are soluble in water All chlorides are soluble, including silver chloride All nitrates are soluble, including lead(II) nitrate All sulfates are soluble except those of potassium and sodium

Quiz: Chemistry - Acid-Base Chemistry