The time taken for the combustion of one piece of coal in air is much greater than for the combustion of powdered coal with the same mass . Explain with reasons.

The rate at which a piece of coal burns is much slower than the rate of burning of powdered coal of equal weight. Explain.

Equal masses of milk and water are taken in two identical kettles and heated by the same source. The ratio of rise of temperature of milk is found to be higher than that of water. Explain.

Mass of one object remains same, but of another object mass is increased 3 times than before and their distance is also increased three times. Then will the gravitational force increase or decrease?

At constant temperature and pressure volume of an ideal gas (molecular mass 28g*mol^(-1) ) is 23.36 times greater than its mole number. Find out its density at the same temperature and pressure.

Out of Cl_(2) and O_(2) , which one will have greater mass when taken in equal volumes at the same temperature nd pressure

At 25^(@)C the heat of combustion at constant volume of 1 mol of a compound is 5150 kJ. The temperature of a bomb calorimeter rises from 25^(@)C to 30.5^(@)C when a certain amount of the compound is burnt in it. If the heat capacity of the calorimeter is 9.76 kJ*K^(-1) then how much of the compound was taken for combustion. [Molar mass of the substance=128]

Two pieces of stone are thrown vertically upwards at the same time. One reaches a height 35 m more than the other and touches the ground 2s later. What are the initial velocities of the stones ? [ g =10 "m.s"^(-2) ]

This question has Statement I and Statement II. Of the four choices given after the Statements, choose the one that best describes the two Statements. Statement-I : All combustion reactions are exothermic. Statement-II : Enthalpies of products are greater than enthalpies of reactants (sumV_PDelta_fH(P) gt sum V_RDelta_f H(R))

One tonne of water is heated from 10^(@)C" to "70^(@)C using coal. The heat of combustion of coal is 1.5xx10^(4)" cal.g"^(-1) . How many kilograms of coal is required if 60% of the heat is utilised in heating water ?