A solution having pH equal to zero is known as
- A.highly alkaline solution
- B.highly acidic solution
- C.weakly acidic solution
- D.neutral solution
Correct answer
Explanation
The correct answer is B, highly acidic solution. The lower the pH, the stronger the acid, and pH 0 lies at the most acidic end of the common scale.
pH is the negative logarithm of the hydrogen ion concentration. A pH of 0 means the hydrogen ion concentration is 1 mole per litre, as in a fairly concentrated solution of hydrochloric acid. Because the scale is logarithmic, each step down by one unit means ten times more hydrogen ions, so a solution of pH 0 is a hundred times more acidic than one of pH 2. On the usual 0 to 14 scale, 7 is neutral and 14 is the most alkaline.
A is wrong: a highly alkaline solution has a pH close to 14, such as strong sodium hydroxide.
C is wrong: a weakly acidic solution has a pH a little below 7, such as rain water or milk.
D is wrong: a neutral solution, such as pure water at 25 °C, has a pH of exactly 7.
Exam tip: below 7 acidic, 7 neutral, above 7 basic; one pH unit means a tenfold change in acidity.
Practice Questions
View allThe speed of the wind is measured by
- A.wind vane
- B.wind rose
- C.barometer
- D.anemometer
Show answer
An anemometer measures how fast the wind is blowing; its name comes from the Greek word anemos, meaning wind.
Read the full explanation →Brilliance of diamond is due to
- A.interference of light
- B.diffraction of light
- C.polarization of light
- D.total internal reflection of light
Show answer
Light that enters a cut diamond is reflected again and again inside it before it escapes, which makes the stone sparkle.
Read the full explanation →Which one of the following is NOT an electromagnetic wave ?
- A.Light wave
- B.Radio wave
- C.Sound wave
- D.Micro wave
Show answer
Sound is a mechanical wave that needs a medium to travel, while the other three are electromagnetic waves. Sound travels as a longitudinal wave of compressions and rarefactions in air, water or solids, which is why it cannot pass through a vacuum.
Read the full explanation →Which one of the following is NOT true for an electromagnetic wave ?
- A.Electromagnetic wave transports energy and momentum
- B.Electromagnetic wave can be polarized and reflected
- C.Electromagnetic wave is longitudinal
- D.Electromagnetic wave propagation is described by the varying electric and magnetic fields
Show answer
Electromagnetic waves are transverse, not longitudinal, so this statement is false. In an electromagnetic wave the electric field and the magnetic field oscillate at right angles to each other and both at right angles to the direction in which the wave travels.
Read the full explanation →Which one of the following frequency ranges is sensitive to human ears ?
- A.0-200 Hz
- B.20-20,000 Hz
- C.200-20,000 Hz only
- D.2,000-20,000 Hz only
Show answer
The normal human ear hears sound from about 20 hertz to 20,000 hertz, the audible range. Frequency, measured in hertz, is the number of vibrations per second, and it decides the pitch of a sound: the higher the frequency, the shriller the note.
Read the full explanation →