The number of hydrogen atoms present in 25.6 g of sucrose (C12H22O11) which has a molar mass of 342.3 g is
22 1023
9.91 1023
11 1023
44 1023 H atoms
The number of formula units of calcium fluoride, CaF2 present in 146.4 g of CaF2 (the molar mass of CaF2is 78.08 g/mol) is
1.129
1.146
7.808
The standard free energy change of a reaction is Calculate the equilibrium constant Kp in log Kp (R =8.314 JK -1mol-1 ).
20.16
2.303
2.016
13.83
If an endothermic reaction occurs spontaneously at constant temperature (T) and pressure (p), then which of the following is true?
A spontaneous process is one in which the system suffer
no energy change
a lowering of free energy
a lowering of entropy
an increase in internal energy
Diamond is hard because
all the four valence electrons are bonded to each carbon atoms by covalent bonds
it is a giant molecule
it is made up of carbon atoms
it cannot be burnt
A.
all the four valence electrons are bonded to each carbon atoms by covalent bonds
In diamond each carbon atom is linked to four other carbon atoms by sigma bond. Each C - C bond is formed by the overlapping of sp3 hybrid orbitals of each carbon atoms. Each carbon atom is present at the centre of a regular tetrahedron. Each carbon atom is surrounded by four other carbon atoms present at the corners of a regular tetrahedron. The octet of each carbon atom is complete. Structure of diamond is a rigid three dimensional network. This explain high density and hardness of diamond. Diamond is chemically inactive due to rigid three dimensional structure.
High energy is required to break the large number of C - C bonds present in diamond. This explain the high melting point of diamond.
The continuous phase contains the dispersed phase throughout, example is
water in milk
fat in milk
water droplets in mist
oil in water