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There were 15 moles of a substance present initially in a system, 25 moles were added to it and a reaction occurred so that its moles are reduced by 50%, what are the final moles of a substance in the system?

Correct Answer: 20
Final moles of substance = (15 + 25)*50/100 = 20.

There were 10 moles of a substance present initially in a system, 5 moles were added to it and a reaction occurred so that its moles are reduced by 20%, what are the final moles of a substance in the system?

A university library budget committee must reduce exactly five of eight areas of expenditure—I, J, K, L, M, N, O and P—in accordance with the following conditions: If both I and O are reduced, P is also reduced.
If L is reduced, neither N nor O is reduced.
If M is reduced, J is not reduced.
Of the three areas J, K, and N exactly two are reduced. Question : If both K and N are reduced, which one of the following is a pair of areas neither of which could be reduced?

For a reaction, the extent of reaction equation is Ni = Nio + ϒVi is Where: Ni = Moles of species I present in the system after the reaction occurs Nio = Moles of species I present in the system when the reaction starts Vi = Stoichiometric coefficient for species i in the specified chemical reaction equation ϒ = Extent of reaction

Read the passage carefully and select the best answer to each question out of the given four alternatives.
The Amazon basin has been continuously inhabited for at least 10, 000 years, possibly more. Its earliest inhabitants were stone-age peoples, living in hundreds of far-flung tribes, some tiny, others numbering in the tens of thousands. It was from the west that Europeans explorers first arrived. In 1541 a Spanish expedition from Quito, led by Gonzalo Pizarro, ran short of supplies while exploring east of the Andes in what is today Peru. Pizarros cousin Francisco de Orellana offered to take 60 men along with the boats from the expedition and forage for supplies. De Orellana floated down the Rio Napo to its confluence with the Amazon, near Iquitos (Peru), and then to the mouth of the Amazon. Along the way his expedition suffered numerous attacks by Indians; some of the Indian warriors, they reported, were female, like the Amazons of Greek mythology, and thus the worlds greatest river got its name. No one made a serious effort to claim this sweaty territory, however, until the Portuguese built a fort near the mouth of the river at Belém in 1616, and sent Pedro Teixeira up the river to Quito and back between 1637 and 1639. During the 17th and 18th centuries, Portuguese bandeirantes (groups of roaming adventurers) penetrated ever further into the rain forest in pursuit of gold and Indian slaves, exploring as far as present-day Rondônia, and the Guaporé and Madeira river valleys. Amazonian Indians had long used the sap from rubber trees to make waterproof bags and other items. European explorers recognized the potential value of natural latex, but were unable to market it because it tended to grow soft in the heat, or brittle in the cold, and thus had limited appeal outside the rain forest. However, in 1842 American Charles Goodyear developed vulcanization (made natural rubber durable) and in 1890 Irelands John Dunlop patented pneumatic rubber tires. Soon there was an unquenchable demand for rubber in the recently industrialized USA and Europe, and the price of rubber on international markets soared. As profits skyrocketed, so did exploitation of the seringueiros, or rubber tappers, who were lured into the Amazon, mostly from the drought-stricken northeast, by the promise of prosperity only to be locked into a cruel system of virtual slavery dominated by seringalistas (owners of rubber-bearing forests). Rigged scales, hired guns, widespread illiteracy among the rubber tappers, and monopoly of sales and purchases all combined to perpetuate the workers debt and misery. In addition, seringueiros had to contend with jungle fevers, Indian attacks and all manner of deprivation.
Where did De Orellano float down to for its confluence with the Amazon?

10 moles of A were present in a system initially, and 10 moles are added to it, it follows the reaction 4A -> B, what are the number of moles of B produced?

10 moles of A were present in a system initially, and 10 moles of C are added to it, it follows the reaction 2A + C -> 5B, what is the number of moles of B produced?

10 moles of A were present in a system initially, and 12 moles of C are added to it, it undergoes the reaction 2A + 3C -> 2B, what are number of moles of B produced?

10 moles of A were present in a system initially, and 8 moles of C are added to it, it undergoes the reaction 5A + 3C -> 4B, what are number of moles of B produced?

8 moles of A were present in a system initially, and 24 moles of B are added to it, it undergoes the reaction 2A + 3B -> 4C + 5D, what are the number of moles of D produced?

Rate constant for a first order reaction does not depend upon reaction time, extent of reaction and the initial concentration of reactants ; but it is a function of reaction temperature. In a chemical reaction, the time required to reduce the concentration of reactant from 100 gm moles/litre to 50 gm moles/litre is same as that required to reduce it from 2 gm moles/litre to 1 gm mole/litre in the same volume. Then the order of this reaction is