CSS - PMS - CCE - PCS - General Science
Chemical Reactions - pH Scale
Which pH value is the most acidic among 2, 5, 7 and 10?
A. 2
B. 7
C. 10
D. 5
Correct Answer: A
Lower pH indicates greater acidity in the conventional range.
CSS - PMS - CCE - PCS - General Science
Chemical Reactions - pH Scale
Which expression defines pH in elementary chemistry?
A. pH = −log10[H+]
B. pH = mass/volume
C. pH = force × distance
D. pH = V/I
Correct Answer: A
pH is defined logarithmically in terms of hydrogen ion activity; concentration is often used in simple treatments.
CSS - PMS - CCE - PCS - General Science
Chemical Reactions - pH Scale
If pH decreases from 6 to 4, hydrogen ion activity increases by approximately what factor?
A. 100
B. 10
C. 2
D. 1000
Correct Answer: A
Two pH units correspond to 10 × 10 = 100 times greater hydrogen ion activity.
CSS - PMS - CCE - PCS - General Science
Chemical Reactions - pH Scale
Which indicator commonly shows a range of colors across different pH values?
A. Distilled water only
B. Sodium metal
C. Universal indicator
D. Iron filings
Correct Answer: C
Universal indicator is a mixture of indicators designed to show a broad pH range.
CSS - PMS - CCE - PCS - General Science
Chemical Reactions - pH Scale
Which instrument gives a more precise pH reading than litmus paper?
A. Calorimeter
B. pH meter
C. Ammeter
D. Barometer
Correct Answer: B
A pH meter uses an electrochemical electrode system to estimate pH accurately.
CSS - PMS - CCE - PCS - General Science
Chemical Reactions - pH Scale
Because pH is logarithmic, a change of one pH unit corresponds approximately to what change in hydrogen ion activity?
A. A factor of 1000 always
B. A factor of 2
C. No change
D. A factor of 10
Correct Answer: D
The pH scale is base-10 logarithmic.
CSS - PMS - CCE - PCS - General Science
Chemical Reactions - pH Scale
A solution with pH 11 is best described as what?
A. Acidic
B. Neutral
C. Basic
D. Radioactive
Correct Answer: C
pH values above 7 are basic.
CSS - PMS - CCE - PCS - General Science
Chemical Reactions - pH Scale
A solution with pH 3 is best described as what?
A. Acidic
B. Metallic
C. Basic
D. Neutral
Correct Answer: A
pH values below 7 are acidic under ordinary classroom conditions.
CSS - PMS - CCE - PCS - General Science
Chemical Reactions - pH Scale
At 25°C, what pH is conventionally considered neutral for pure water?
A. 7
B. 14
C. 1
D. 0
Correct Answer: A
At 25°C, neutral water has pH about 7.
CSS - PMS - CCE - PCS - General Science
Chemical Reactions - pH Scale
What does the pH scale primarily measure?
A. Electrical resistance
B. Mass density
C. Acidity or basicity related to hydrogen ion activity
D. Atomic number
Correct Answer: C
pH is a logarithmic measure related to hydrogen ion activity in a solution.