Grade 10 general science – Acids, Bases and Salts Quiz

Acids often react with active metals (like zinc or magnesium) to produce hydrogen gas. Bitter taste and slippery feel are typical of bases. Acids turn blue litmus red, not the other way round. A soapy texture is a property of bases.

Vinegar contains acetic acid, a weak acid commonly used in cooking and cleaning. Sodium hydroxide and ammonia are basic, while sodium bicarbonate is a mild base (basic salt).

Blue litmus turns red in the presence of an acid. Remaining blue indicates neutral or basic, green is not a standard litmus result, and colourless is not correct for litmus indicators.

Bases typically turn red litmus blue and often feel slippery due to saponification of skin oils. Donating protons describes acids. Reaction with acids gives salt and water, not oxygen. Neutral substances have pH 7.

When HCl (acid) reacts with NaOH (base) they neutralize to form the salt NaCl and water. Calcium hydroxide is a base formed by hydration, water formation here is not a salt, and ammonia is not a neutralisation product.

Universal indicator is a mixture that shows a range of colours corresponding to pH values, allowing approximate pH estimation. Single indicators like phenolphthalein or methyl orange show only specific endpoint colour changes, and litmus gives only acidic or basic result.

At 25°C pure water is neutral and has pH 7. pH 0 and 1 are strongly acidic, and 14 is strongly alkaline.

H2SO4 neutralised by NaOH produces sodium sulphate (Na2SO4) and water. Sodium carbonate and sodium chloride are from different acids/bases, and calcium sulphate involves calcium, not sodium hydroxide.

Acid reacting with carbonates produces carbon dioxide gas, water and a salt. Oxygen and nitrogen are not produced in this reaction; hydrogen is released when acids react with metals, not carbonates.

Lime is alkaline and is applied to acidic soils to raise pH and improve nutrient availability. It does not increase acidity or salinity, and while it may affect microbes, its main purpose is neutralisation and fertility improvement.

Antacids are basic compounds that neutralise excess stomach acid (HCl), producing salts and water, which reduces acidity and pain. They do not increase acid, act as oxidisers, or convert acid into a gas.

Sodium hydroxide is a strong base used in saponification to make soap from fats. Hydrochloric and acetic acids are acids, and sodium chloride is a salt, not a base.

Adding acid to water increases hydrogen ion concentration, lowering the pH below 7 and making the solution acidic. pH will not increase or remain neutral when acid is added.

Phenolphthalein changes near the pH where a weak acid is neutralised by a strong base, showing a clear end-point (colourless to pink). Methyl orange is better for strong acid-strong base titrations; blue litmus is not precise enough and you need an indicator for titration.

Neutralisation of ethanoic (acetic) acid by NaOH forms sodium ethanoate (sodium acetate) and water. The other options are unrelated to this neutralisation.

Smelling chemicals directly is dangerous and not allowed. Proper precautions include wearing PPE, adding acid to water during dilution, and working in ventilated spaces.

HCl reacts with CaCO3 to produce calcium chloride (a salt), carbon dioxide and water. Sodium and potassium chlorides involve sodium or potassium, and calcium hydroxide is a base, not the salt produced here.

Strength of an acid refers to degree of ionisation in water: weak acids partially ionise, strong acids largely or completely ionise. Physical state and violence of reaction are not correct descriptors; litmus colour comments are reversed and incorrect.

Sodium chloride is present in sweat and is essential for electrolyte balance. The other compounds are not the main salt in sweat.

Methyl orange turns red in acidic solutions (pH < about 3.1). It is yellow in neutral to basic solutions. Sodium hydroxide is basic and would not give red.

Neutralisation yields a salt and water. Hydrogen gas is produced when acids react with certain metals, not in neutralisation with bases. Oxygen or metal formation are not general results of acid-base neutralisation.

Sodium bicarbonate can neutralise acids (act as a base) and in some reactions can act as a weak acid; it is commonly used in baking and cleaning. Sodium chloride is neutral, HCl is an acid, and NaOH is a strong base.

The known base (titrant) is added to neutralise the unknown acid; from the volume used one can calculate the acid concentration. It is not an indicator or solvent and it is clearly involved in the reaction.

Sodium chloride is common table salt used for seasoning and preservation. Potassium permanganate is an oxidiser, magnesium sulphate is Epsom salt, and calcium hydroxide is lime.

NH3 + HCl → NH4Cl, ammonium chloride is the salt formed. Water is not the only product, and sodium or calcium chlorides require those metals.

Soap (a base) typically feels slippery due to its alkaline nature and may taste soapy (not recommended to taste chemicals), while vinegar is acidic and tastes sour but is not slippery. Note: tasting chemicals is unsafe; this question assumes safe, controlled household recognition and discourages tasting in labs.

Adding acid to water slowly controls the exothermic heat release and prevents dangerous splattering of concentrated acid. Adding water to acid can cause violent boiling and splashing. It does not make the acid stronger.