White coal is a form of fuel produced by drying chopped wood over a fire. It differs from charcoal which is carbonised wood. White coal was used in England to smelt lead ore from the mid-sixteenth to the late seventeenth centuries. It produces more heat than green wood but less than charcoal and thus prevents the lead evaporating. White coal could be use mixed with charcoal for other industrial uses than lead smelting. White coal was produced in distinctive circular pits with a channel, known as Q-pits. They are frequently found in the woods of South Yorkshire.

Correct Option: E

White coal is a form of fuel produced by drying chopped wood over a fire. It differs from charcoal which is carbonised wood. White coal was used in England to smelt lead ore from the mid-sixteenth to the late seventeenth centuries. It produces more heat than green wood but less than charcoal and thus prevents the lead evaporating. White coal could be use mixed with charcoal for other industrial uses than lead smelting. White coal was produced in distinctive circular pits with a channel, known as Q-pits. They are frequently found in the woods of South Yorkshire.

The pH scale measures how acidic or basic a substance is. The pH scale ranges from 0 to 14. A pH of 7 is neutral. A pH less than 7 is acidic. A pH greater than 7 is basic. The pH scale is logarithmic and as a result, each whole pH value below 7 is ten times more acidic than the next higher value.

Correct Option: C

The pH scale measures how acidic or basic a substance is. The pH scale ranges from 0 to 14. A pH of 7 is neutral. A pH less than 7 is acidic. A pH greater than 7 is basic. The pH scale is logarithmic and as a result, each whole pH value below 7 is ten times more acidic than the next higher value.

The atomic mass (A) of Uranium (92U238) = 238; the number of protons (p) = 92 = number of electrons (e). Since atomic mass (A) = p + n (number of neutrons), A = 238 = 92 + n So, n = 238 -92 = 146

Correct Option: C

The atomic mass (A) of Uranium (92U238) = 238; the number of protons (p) = 92 = number of electrons (e). Since atomic mass (A) = p + n (number of neutrons), A = 238 = 92 + n So, n = 238 -92 = 146

Helium is used by deep sea divers because it reduces the narcosis of nitrogen and it remains below the oxygen toxicity limits. In fact, they use tri mix of Oxygen, helium and a little bit of nitrogen.

Correct Option: D

Helium is used by deep sea divers because it reduces the narcosis of nitrogen and it remains below the oxygen toxicity limits. In fact, they use tri mix of Oxygen, helium and a little bit of nitrogen.

Two oxygen atoms can both achieve stable structures by sharing two pairs of electrons as in the diagram. Two electrons of each of the atom in the oxygen molecule make the double bond with each other. The double bond is shown conventionally by two lines joining the atoms. Each line represents one pair of shared electrons.

Correct Option: B

Two oxygen atoms can both achieve stable structures by sharing two pairs of electrons as in the diagram. Two electrons of each of the atom in the oxygen molecule make the double bond with each other. The double bond is shown conventionally by two lines joining the atoms. Each line represents one pair of shared electrons.