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- Arrange the following fractions in descending order.
Arrange the following fractions in descending order.
Date posted: February 26, 2019
- The cost of a pen is sh.X and that of a pencil is sh. 4 less than that of a pen. Find the combined cost of 4 pens and 5 pencils.
The cost of a pen is sh.X and that of a pencil is sh. 4 less than that of a pen. Find the combined cost of 4 pens and 5 pencils.
Date posted: February 26, 2019
- Factorize: 6x2 -13x + 6
Factorize: 6x2 -13x + 6
Date posted: February 26, 2019
- During heating of a hydrated copper (II)sulphate crystals, the following readings were obtained:
Mass of evaporating dish =300.0g, Mass of evaporating dish + hydrated salt = 305.0g, Mass of evaporating dish + anhydrous salt = 303.2g
During heating of a hydrated copper (II)sulphate crystals, the following readings were obtained:
Mass of evaporating dish =300.0g, Mass of evaporating dish + hydrated salt = 305.0g, Mass of evaporating dish + anhydrous salt = 303.2g
Calculate the number of water of crystallization molecules in hydrated copper (II)sulphate.(Cu =64.5, S = 32.0,O=16.0, H = 1.0)
Date posted: February 26, 2019
- An element Q consists of 3 isotopes of mass 28, 29, 30 and percentage abundance of 92.2%, 4.7%, 3.1% respectively. Determine the relative atomic mass of the element?
An element Q consists of 3 isotopes of mass 28, 29, 30 and percentage abundance of 92.2%, 4.7%, 3.1% respectively. Determine the relative atomic mass of the element?
Date posted: February 26, 2019
- An element N forms an ion N2. This ion contains 18 electrons:
a) State the period and the group of the periodic table that element N belongs.
An element N forms an ion N2. This ion contains 18 electrons:
a) State the period and the group of the periodic table that element N belongs.
b) Write the formula of the compound which would be formed if N reacts with bromine.
Date posted: February 26, 2019
- When 27.8g of hydrated aluminium oxide, Al2O3.xH2O, was heated to a constant mass, 20.6g of aluminium oxide was obtained. Determine the value of x (H=1, O=16, A=27)
When 27.8g of hydrated aluminium oxide, Al2O3.xH2O, was heated to a constant mass, 20.6g of aluminium oxide was obtained. Determine the value of x (H=1, O=16, A=27)
Date posted: February 26, 2019
- 6g of iron reacted with hydrogen chloride gas to form iron (II) chloride at S.T.P. Calculate the volume of the hydrogen chloride
gas used. (Fe=56, molar gas volume at S.T.P=22.4dm3 )
6g of iron reacted with hydrogen chloride gas to form iron (II) chloride at S.T.P. Calculate the volume of the hydrogen chloride
gas used. (Fe=56, molar gas volume at S.T.P=22.4dm3 )
Date posted: February 26, 2019
- Study the information in the table below and answer the questions that follow.
Study the information in the table below and answer the questions that follow.
i) Write the general formula of the hydrocarbons in the table.
ii) Predict the relative molecular mass of the hydrocarbon with 5 carbon atoms.
iii) Determine the molecular formula of the hydrocarbon in (II) above and draw its structural formula (H=1.0, C = 12.0)
Date posted: February 26, 2019
- An organic compound contains 24.24% carbon 4.04% hydrogen and the rest is chlorine
a) Find its empirical formula. (C=12, H=1, Cl=35.5)
b) Find its molecular formula if its R.M.M is 99.
An organic compound contains 24.24% carbon 4.04% hydrogen and the rest is chlorine
a) Find its empirical formula. (C=12, H=1, Cl=35.5)
b) Find its molecular formula if its R.M.M is 99.
Date posted: February 26, 2019
- Using dots (.) and crosses (x) to represent outermost electrons, draw diagrams to show bonding in.
a)Carbon (IV) oxide
b) NH4+
Using dots (.) and crosses (x) to represent outermost electrons, draw diagrams to show bonding in.
a)Carbon (IV) oxide
b) NH4+
Date posted: February 26, 2019
- Chlorine is element number 17 in the periodic table of elements. Write down the electron configuration of its:
a) Atom
b) Ion
Chlorine is element number 17 in the periodic table of elements. Write down the electron configuration of its:
a) Atom
b) Ion
Date posted: February 26, 2019
- An atom of sodium is represented as shown below: (a) Calculate the number of neutrons in the nucleus of a sodium atom
An atom of sodium is represented as:
a) Calculate the number of neutrons in the nucleus of a sodium atom.
b)Write the electronic configuration of a sodium atom
Date posted: February 26, 2019
- Zinc metal and hydrochloric acid react according to the following equation: Zn(s) + 2Hcl(aq)= ZnCl2(aq) + H2(g)
Zinc metal and hydrochloric acid react according to the following equation:
Zn(s) + 2Hcl(aq) = ZnCl2(aq) + H2(g)
1.96g of zinc metal were reacted with 100cm3 of 0.2m hydrochloric Acid.
a) Determine the reagent that was in excess.
b) Calculate the total volume of hydrogen gas that was liberated at S.T.P. Zn=65.4; molar gas volume = 22.4 litres at S.T.P.
Date posted: February 26, 2019
- Write an equation to show the effect of heat on:
i) Potassium nitrate, KNO3
ii) silver nitrate, AgNO3
Write an equation to show the effect of heat on:
i) Potassium nitrate, KNO3
ii) silver nitrate, AgNO3
Date posted: February 26, 2019
- Calculate the percentage nitrogen content in the following ammonium salts.
i) Ammonium sulphate (NH4)2SO4
ii) Urea, (NH2)2CO
N= 14, H=1, S=32, O=16, C=12
Calculate the percentage nitrogen content in the following ammonium salts.
i) Ammonium sulphate (NH4)2SO4
ii) Urea, (NH2)2CO
N= 14, H=1, S=32, O=16, C=12
Date posted: February 26, 2019
- 4.0g of magnesium carbonate have some impurity of magnesium sulphate were dissolved in 250cm3 of 1.0m HCL. 25cm3 of the resulting solution was found to require 28.8cm3 of 0.6M sodium hydroxide for complete neutralization.Calculate the number of moles of sodium hydroxide in 28.8cm3.
4.0g of magnesium carbonate have some impurity of magnesium sulphate were dissolved in 250cm3 of 1.0m HCL. 25cm3 of the resulting solution was found to require 28.8cm3 of 0.6M sodium hydroxide for complete neutralization.Calculate the number of moles of sodium hydroxide in 28.8cm3.
Date posted: February 26, 2019
- Draw the structural formulae of the following compounds:
a) 2, 3 – dibromobutane
b) 2, 3, 4 – trimethyl pentene
c) 4 – chloro – 5 – methylhex – 2 –yne
Draw the structural formulae of the following compounds:
a) 2, 3 – dibromobutane
b) 2, 3, 4 – trimethyl pentene
c) 4 – chloro – 5 – methylhex – 2 –yne
Date posted: February 26, 2019
- Balance the chemical equation given below
C3H8 + O2 ?H2O + CO2
Balance the chemical equation given below
C3H8 + O2 ?H2O + CO2
Date posted: February 26, 2019
- 30cm3 of hydrogen chloride gas diffuses through a porous pot in 20 seconds. How long would it take 42cm3 of sulphur(IV) oxide gas to diffuse through the same pot under the same conditions (H =1 Cl = 35.5 S = 32 O =16)
30cm3 of hydrogen chloride gas diffuses through a porous pot in 20 seconds. How long would it take 42cm3 of sulphur(IV) oxide gas to diffuse through the same pot under the same conditions (H =1 Cl = 35.5 S = 32 O =16)
Date posted: February 26, 2019