Question

Silicon has three naturally occurring isotopes with thefollowing masses and natural abundances:

Answer 1

Answer:

See explanation

Explanation:

Relative atomic mass of silicon;

(27.9769  ×  0.9218)  +  (28.9765  ×  0.0471)  +  (29.9738  ×  0.0312) = 28.0891

2)

2AgNO3 (aq) + CaCl2(aq) ----> 2AgCl(s) + Ca(NO3)2(aq)

number of moles of silver nitrate = 1.18 L * 0.113 M = 0.133 moles

Since 2 moles of silver nitrate yields 2 moles of silver chloride

0.133 moles of silver nitrate yields 0.133 * 2/2 = 0.133 moles of AgCl

Since 2 moles of silver nitrate reacts with 1 mole of calcium chloride

0.133 moles of silver nitrate reacts with  0.133 moles * 1/2 = 0.0665 moles of CaCl2

n =CV

C =n/V = 0.0665 moles/3.28 L = 0.02 M

3) H2SO4(aq) + 2KOH(aq) -------> K2SO4(aq) + 2H20(l)

CA = concentration of acid = 1.5 M

VA = volume of acid  23.7 ml

CB = concentration of base = ?

VB= volume of base = 50 ml

NA = number of moles of acid =1

Number of moles of base = 2

From;

CAVA/CBVB =NA/NB

CAVANB = CBVBNA

CB = CAVANB/VBNA

CB = 1.5 * 23.7 * 2/ 50 * 2

CB = 0.711 M

4) Number of moles of KMnO4 = 1.68 * 19.8/1000 = 0.033 moles

If 2 moles of KMnO4 reacts with 1 mole of H2O2

0.033 moles of KMnO4 reacts with  0.033 * 1/2 = 0.0165 moles of H2O2

molar mass of H2O2 = 34 g/mol

mass of H2O2 = 0.0165 moles of H2O2 * 34 g/mol = 0.56 g of H2O2