100 mL of a water sample contains 0.81 g of calcium bicrabonate and 0.73 g of magnesium bicarbonate. The hardness of this water sample expressed in terms of equivalents of CaCO₃ is : (Molar mass of calcium bicarbonate is 162 g mol^–1 and magnesium bicarbonate is 146 g mol^–1)

The quantum number of four electrons are given below :
n = 4, l = 2, m_l =–2, m_s = –1/2
n = 3, l = 2, m_l = 1, m_s = +1/2
n = 4, l = 1, m_l = 0, m_s = +1/2
n = 3, l = 1, m_l = 1, m_s = –1/2
The correct order of their increasing enegies will be :

Which of the following amines can be prepared by Gabriel phthalimide reaction ?

Which one of the following equations does not correctly represent the first law of thermodynamics for the given processes involving an ideal gas? (Assume non-expansion work is zero)