A radiation detector on a laboratory bench is switched on when there are no radioactive samples in the laboratory. The count rate displayed by the detector is 24 counts per…

The industrial manufacture of ethanol from ethene is a catalysed reversible reaction. The equation for this reaction is:C2H4(g) + H2O(g)֖ C2H5OH(g) ΔH = – 46 kJ mol –1Which of the…

The browning of fruit involves enzymes. The time taken for slices of apple kept in different solutions to turn brown is shown in the table. The effect of pH and…

Express the following in its simplest form : 3xy (x3 / y4 )2 Answer:

An object of mass 5.0 kg falls vertically through still air. The air resistance acting on the object has a constant value of 50 N. Which of the following statements…

Element Z forms a stable ion Z3– which has the electron configuration 2,8,8. To which Group and Period of the Periodic Table does Z belong? Answer: 2) D The ion…

A person with cardiovascular disease is at risk of a heart attack. A blood clot may form in one of the arteries that supplies blood to the heart muscle. If…

A bar magnet is rotating at a constant rate of 120 revolutions per minute inside a circular coil of wire, causing an induced voltage across the coil. Which of the…

Diammonium hydrogen phosphate, (NH4)2HPO4, can be used as a fertiliser. The following equation shows how it can be synthesised:2NH3(g) + H3PO4(aq) → (NH4)2HPO4(s)What is the mass of diammonium hydrogen phosphate…

The diagram shows part of a DNA double helix being copied Which of the following statements, considered independently, is/are correct?1 The probability of any base in strand 2 being guanine…