26- the correct answer is ( D )18
27- the correct answer is D 18 atoms
28- the correct answer is B 4
29- the correct answer is D Zn + 2HCl→ ZnCl2 + H2
30-∴ the correct answer is B 2
31- the correct answer is D 10
32- the correct answer is C 2
33- the correct answer is D HCl is the limiting reactant, 5.8 mol of H2 can be formed
34- the correct answer is B 20.6 g
35- the correct answer is C 35.88 g
36- the correct answer is D 277 g
37- the correct answer is C
38- the correct answer is C 2,1,1,2
39- the correct answer is A) K2SO4 + 2 Ca(NO3)2→ 2KNO3 + 2CaSO4
40- The correct answer is (A ) K2S + COCl2→ 2 KCl + COS
41- the correct answer is (B) water (H2O) is always a product
42- the correct answer is B 2.2 mol
43- the correct answer is (C) Al is the limiting reactant, 5.3 moles of H2 can be formed
44- the correct answer is (D ) 6.8 moles
45- the correct answer is A 75.4 %
Que26
The number of oxygen atoms 18 atoms of oxygen ( answer D)
calculation
count the number of oxygen atoms in Ba(ClO3)2
that is = 3 x2 = 6 atoms
then multiply by 3 since there are 3 molecules of Ba(ClO3)2
that = 6 x3 = 18 atoms of oxygen
Que 27
The number of atoms of oxygen is 18 atoms of Oxygen ( answer D)
calculation
Step 1: count the number of oxygen atoms in Fe(NO3)2
that is = 3 x2 = 6 atoms of Oxygen
Step 2: multiply by total number of Fe(NO3)2 molecules ( 3 molecules)
that is , 6 x3 = 18 atoms of oxygen
question 28
The coefficient in front of H2O is 4 ( answer 8)
Explanation
Balance the equation
= 3 Fe + 4 H2O → Fe3O4 + 4 H2
therefore the coefficient in front of H2O = 4
que 29
The balance chemical equation is
Zn + 2HCl→ ZnCl2 +H2 ( answer D)
Explanation
Zn + 2HCl→ ZnCl2 + H2 is balanced since it obey the law of mass conservation.
Que 30
The coefficient in front of HNO3 is 2 ( answer B)
Explanation
balance the equation of N2O5 + H2O→ 2HNO3
Therefore the coefficient in front of HNO3 is 2
Que 31
The number of atoms of Hydrogen is 10 atoms ( answer D)
Calculation
Step 1: count the number of H atoms in CH3CH2O
= 3 +2= 5 atoms
Step 2: multiply 5 atoms by 2 ( coefficient in front of CH3CH2O)
= 5 atoms x 2 = 10 atoms
Ques 32
The moles of Oxygen gas needed is 2 moles ( answer C)
Explanation
= 4 Li +O2 → 2Li2O
The mole ratio of Li :O2 = 4:1
therefore the moles of Oxygen = 8 moles x1/4 = 2 moles
Que 33
The limiting reactant is HCl and 5.8 moles of H2 can be formed
Explanation
to determine the limiting reagent
Al : AlCl3 is 2 :2 = 1:1 therefore the moles of AlCl3 = 4.5 moles
HCl: AlCl3 = 6:2 therefore the moles of Al2Cl3 = 11.5 x2/6= 3.8 moles
therefore HCl is the limiting reagent since it is totally consumed
moles of HCl formed
The mole ratio of HCl: H2 = 6:3 therefore the moles of H2 = 11.5 x 3/6 = 5.8 moles
que 34
The grams of oxygen gas = 20.6 g O2( answer A)
explanation
calculate the moles of LiClO3
= 38.7 g / 90.38 g/mol=0.428 moles
by use of mole ratio of of LiClO3: O2= 2:3 the moles of O2
= 0.428 x3/2=0.642 moles
mass =moles x molar mass
= 0.642 moles x 32 g/mol= 20.6 g O2
Ques 35
The grams of silicon nitride that can be formed is 35.88 g( answer C)
calculation
find the moles of nitrogen
= 14.33 g/ 28 g/mol=0.512 moles
N2: Si3N4 is 2:1 the moles of SiN4
= 0.512 moles x 1/2=0.256 moles
find the grams of Si3N4
= 0.256 moles x 140.28 g/mol = 35.91 g which is around 35.88 (answer c)
Que 36
The grams of phosphorus trichloride that can be formed is is 176 g ( answerB)
calculation
moles of P4 = 62.4 g / 123.90 g/mol =0.504 moles
moles of cl2 = 136.2/71 g/mol =1.918 moles
P4 : PCl3 is 1:4 therefore the moles of PCl3 = 0.504 x 4=2.016 moles
Cl2 : PCl3 is 6:4 therefore the moles of PCl3= 1.918 moles x 4/6=1.279 moles
Cl2 is the limiting reagent therefore the moles of PCl3 = 1.279 moles
find the mass of PCl3
= 1.279 moles x 137.33 g/mol =176 g
Que 37
The truth about physical properties is The physical properties include properties like density, melting point, and ductility
Explanation
Physical properties are be measure or observed without changing the composition of matter.
Que 38
The coefficient that must be added to balance the equation are
2,1,1,2 ( answer c)
Explanation
The mass of the product is equal to mass of the reactant when the equation is balanced..
que 39
The chemical equation that violates the law of mass conservation of mass is K2SO4 +2Ca(NO3)2→ 2KNO3 + 2CaSO4 ( answer A)
Explanation.
K2SO4 + 2Ca(NO3)2 → 2KNO3 + 2CaSO4 violate this law because the mass of reactant is not equal to mass of product.
For example in )2 there is 16 atoms of aO2 in reactant side while at product side they are 14 atoms.
Que 40
The double replacement reaction is
K2S + CoCl2→ 2KCl + COS ( answer A)
Explanation
in Double replacement the cation and anion of the two reactant switch places to form new compound.
