A cleaning solution is used to remove limescale, CaCO 3, from bathroom surfaces. When the solution is sprayed onto the limescale, effervescence (fizzing) occurs and the solid limescale begins to…

The diagram shows some stages involved in genetic engineering. Which row correctly identifies W, X, Y and Z? Answer: 1) E W is a section of the chromosome. It is…

The radioactive isotope carbon-14 is found in living material in small quantities. There areapproximately 1000 carbon-14 atoms for every 10 15 carbon-12 atoms. Whilst the material is stillliving this ratio…

Xenon gas reacts with fluorine gas to form gaseous xenon hexafluoride at high temperatureand pressure. The overall energy change is − 330 kJ / mol.Under these conditions, the F –…

In a type of fruit fly the brown body colour allele is dominant to the black body colour allele. A male fruit fly heterozygous for body colour and a female…

Which one of the following is a simplification of x/x-1 - x2+3/ x2 +2x-3? Answer:

The radioactive isotope plutonium-244 becomes radon-220 after a succession of decays. The atomic number of plutonium is 94 and the atomic number of radon is 86. How many alpha particles…

A compound of oxygen and fluorine has a relative molecular mass which is twice that of its empirical formula mass. 105 g of the compound contains 57 g of fluorine.…

An animal cell is surrounded by a very dilute glucose solution which has a lower concentration of glucose than the glucose solution in the cytoplasm of the cell. There is…

The mean mass of a sweet in a bag of 20 sweets must be greater than 10 grams but not greater than 10.5 grams. A bag is being filled with…