Chemistry Past Questions and Answers

What is the number of moles of NaHCO₃in 250cm³ of its solution if the solution contains 8.4 g of NaHCO₃ in 1 dm³ of the solution. [Na = 23, 0 = 16, C = 12, H = 1)

A 1
B 0.25
C 0.05
D 0.025
E 0.01

Question 67:

Which statement is NOT true about the composition of starch?

A It contains only the atoms of carbon, hydrogen oxygen
B It is a polysaccharide
C Its empirical formula is C₂H₂0.
D It is made from the monomerC₆H₁₂O₆.
E The hydrogen and oxygen atoms are in the ratio 2:1.

Question 68:

Chlorine is used in water purification because it ____________

A Bleaches impurities in the water
B Decolorizes water
C Destroys bacteria
D Is extremely soluble in water
E Is pleasant tasting

Question 69:

The number of hydrogen ions in 1.0dm6.00x10³ of a 0.25 mole dm6.00x10^-3 tetraoxosulphate(Vl) acid solution is
[Avogadro constant = 6.0 x 1 0]

A 1.45x10²³
B 1.50 x l0²³
C 3.00x10²³
D 3.15x10²³
E 6.00x10²³

Question 70:

B is an isotope of the element \(^{238} _{92}Ur\). The isotope B has ____________

A 46 protons and 119 neutrons
B 92 protons and 92 neutrons
C 92 protons and 146 neutrons
D 92 protons and 238 neutrons