Which one of the following is the correct order of pH for the given substances?
[amp_mcq option1=”Coffee < Lemon juice < Milk of magnesia < Blood" option2="Milk of magnesia < Blood < Coffee < Lemon juice" option3="Lemon juice < Blood < Milk of magnesia" option4="Lemon juice < Coffee < Blood < Milk of magnesia" correct="option4"]
This question was previously asked in
UPSC CDS-1 – 2023
Approximate pH values for the given substances:
– Lemon juice: pH is typically around 2-2.5 (highly acidic).
– Coffee: pH is typically around 4.5-5 (acidic).
– Blood: pH is slightly alkaline, maintained within a narrow range of 7.35-7.45.
– Milk of magnesia (Magnesium hydroxide, Mg(OH)₂ suspension): A base, pH is typically around 10-11 (basic).
Ordering these substances from most acidic (lowest pH) to most basic (highest pH):
Lemon juice (pH ~2) < Coffee (pH ~5) < Blood (pH ~7.4) < Milk of magnesia (pH ~10.5). Checking the options, option D follows this order.
– Higher pH values indicate higher basicity (alkalinity).
– Pure water has a neutral pH of 7.