Live practice

Displacement occurs only when the added metal is more reactive than the metal ion in solution. B displaces iron, so B is more reactive than iron; it does not displace zinc, so it is below zinc. This makes B the most reactive of A-D.

Because B is above iron and copper, it displaces copper from copper(II) sulphate; the blue solution fades and reddish-brown copper is deposited.

A displaces copper but C does not, so A is above C. C displaces silver, while D displaces none. Therefore:

Hydrogen chloride and nitric acid ionise in water and produce hydronium ions:

Glucose and alcohol contain hydrogen atoms, but they remain as neutral molecules in water and do not release \(\ce{H+}\) or form \(\ce{H3O+}\). Hence their solutions do not show acidic behaviour.

Principle. Constant force gives constant acceleration, found from the change of velocity per time.

Principle. Gravity remains vertically downward throughout. Apply constant-acceleration kinematics with a consistent sign convention.

Compare their least counts. Visible-light wavelength is much smaller than mechanical least counts.

Define the sample space and count each favourable outcome once.

The final value lies in [0,1]; complement pairs also sum to one, providing an independent check.

Form the required totals explicitly and divide by the full number of observations.

The variance is nonnegative and the reported standard deviation is its positive square root.

Simplify the expression before substitution and preserve one-sided information.

Substitution into the original expression verifies the stated domain and final value.

Translate every condition into an equation and retain exact values throughout the straight-line calculation.

The last line satisfies the original conditions and supplies every requested part.

Use the sequence definition or geometric-progression formula, keeping the first-term offset explicit.

The displayed substitutions cover every requested part and verify the result against the original data.