- In an experiment to separate a mixture of water (100oC) and ethanol (78.4oC), a student set up the apparatus shown below.(Solved)
In an experiment to separate a mixture of water (100oC) and ethanol (78.4oC), a student set up the apparatus shown below.
(a) Identify the mistakes in the set up.
(b) What method would the student use to test the purity of ethanol obtained?
Date posted: August 16, 2019. Answers (1)
- Ammonia nitrate is one of the nitrogenous fertilizers manufactured from nitrogen compounds.(Solved)
Ammonia nitrate is one of the nitrogenous fertilizers manufactured from nitrogen compounds.
(a) Identify the reagents used to manufacture ammonium nitrate.
(b) Calculate the percentage of nitrogen in ammonium nitrate fertilizer.(N = 14, H = 1, O =16)
Date posted: August 14, 2019. Answers (1)
- Nitrogen may be isolated from air or from the reaction between ammonium chloride and sodium nitrite.(Solved)
Nitrogen may be isolated from air or from the reaction between ammonium chloride and sodium nitrite.
(a) (i) State the condition necessary for the production of nitrogen from ammonium chloride and sodium nitrite.
(ii) Write an equation for the reaction above.
(b) Name a major impurity contained in nitrogen isolated from air.
Date posted: August 14, 2019. Answers (1)
- Calculate the number of aluminum ions in 250 cm3 of 0.1 M aluminium sulphate (Avogadro’s Constant = 6.0 × 1023)(Solved)
Calculate the number of aluminum ions in 250 cm3 of 0.1 M aluminium sulphate (Avogadro’s Constant = 6.0 × 1023)
Date posted: August 14, 2019. Answers (1)
- Study the information given below for magnesium and calcium.(Solved)
Study the information given below for magnesium and calcium.
(a) Explain the trend in ionisation energies between magnesium and calcium.
(b) Explain why the two elements have higher 2nd ionisation energies than the 1st one.
Date posted: August 14, 2019. Answers (1)
- Use the bond energy values given below to determine the enthalpy change for the conversion of propene to propane by hydrogenation.(Solved)
Use the bond energy values given below to determine the enthalpy change for the conversion of propene to propane by hydrogenation.
Date posted: August 14, 2019. Answers (1)
- Using reagents provided, explain how you could prepare dry zinc carbonate solid.
Zinc powder, dilute nitric (V) acid, Water and Solid sodium carbonate(Solved)
Using reagents provided, explain how you could prepare dry zinc carbonate solid.
Zinc powder, dilute nitric (V) acid, Water and Solid sodium carbonate
Date posted: August 14, 2019. Answers (1)
- In an experiment, iron was heated in the presence of excess oxygen and the following data was obtained.(Solved)
In an experiment, iron was heated in the presence of excess oxygen and the following data was obtained:
Mass of empty crucible = 10.98 g
Mass of crucible + iron before reaction = 12.66 g
Mass of crucible + iron after heating = 13.30 g
Calculate the empirical formula of the oxide of iron. (Fe =56, O = 16)
Date posted: August 14, 2019. Answers (1)
- Below is a list of oxides.(Solved)
Below is a list of oxides.
Select:
(a) A neutral oxide
(b) A highly water soluble basic oxide.
(c) An oxide which can react with sodium hydroxide and dilute hydrochloric acid.
Date posted: August 14, 2019. Answers (1)
- An oxide of Nitrogen was bubbled into a solution of sodium hydroxide in which phenolphthalein indicator has been added. The solution turned colourless after sometime.(Solved)
An oxide of Nitrogen was bubbled into a solution of sodium hydroxide in which phenolphthalein indicator has been added. The solution turned colourless after sometime.
(a) Name the oxide.
(b) Write an ionic equation for the reaction that took place.
Date posted: August 14, 2019. Answers (1)
- Study the flow chart below and answer the questions that follow.(Solved)
Study the flow chart below and answer the questions that follow.
(a) Identify N and P.
(b) Name the type of reaction in step 2.
Date posted: August 14, 2019. Answers (1)
- When heated in a current of nitrogen gas, magnesium reacts to form a compound.(Solved)
When heated in a current of nitrogen gas, magnesium reacts to form a compound.
(a) Write the chemical equation of the compound formed.
(b) Calculate the volume of nitrogen at s.t.p required to react with 0.72 g of magnesium.
(Mg = 24, molar gas volume at s.t.p = 22.4 dm3)
Date posted: August 14, 2019. Answers (1)
- An element P contains two isotopes
whose relative abundance is in the ratio 9:1. Find the relative atomic mass of P.(Solved)
An element P contains two isotopes whose relative abundance is in the ratio 9:1. Find the relative atomic mass of P.
Date posted: August 14, 2019. Answers (1)
- Study the equation below and answer the question that follows.(Solved)
Study the equation below and answer the question that follows.
Identify the acid in the forward reaction. Give a reason for your answer.
Date posted: August 14, 2019. Answers (1)
- A 10 cm3 volume concentrated hydrochloric acid of density 1.18 g/cm3 and purity of 36 percent dissolved in 250 cm3 of distilled water. Calculate the...(Solved)
A 10 cm3 volume concentrated hydrochloric acid of density 1.18 g/cm3 and purity of 36 percent dissolved in 250 cm3 of distilled water. Calculate the morality of the solution. (H = 1, Cl = 35.5)
Date posted: August 14, 2019. Answers (1)
- Archeologists can determine the age of organic matter by measuring the proportion of carbon-14 present in a sample. Assuming that carbon-14 has a half- life...(Solved)
Archeologists can determine the age of organic matter by measuring the proportion of carbon-14 present in a sample. Assuming that carbon-14 has a half- life of 5600 years, calculate the age of a piece of wood found to contain 
as much carbon-14 as in a living material.
Date posted: August 14, 2019. Answers (1)
- Explain the observation made in the experiment whose set up is shown below.(Solved)
Explain the observation made in the experiment whose set up is shown below.
Date posted: August 14, 2019. Answers (1)
- Element G and T have atomic number 20 and 9, respectively.(Solved)
Element G and T have atomic number 20 and 9, respectively.
(a) Write down the electron arrangement of the ion of G.
(b) Which element has the same electron arrangement as the ion of T?
(c) Write the formula of compound formed by reaction of G and T.
Date posted: August 14, 2019. Answers (1)
- An Element X has first, second and third ionization energies. State and explain how their trends compare.(Solved)
An Element X has first, second and third ionization energies. State and explain how their trends compare.
Date posted: August 5, 2019. Answers (1)
- Why is an atom said to be electrically neutral?(Solved)
Why is an atom said to be electrically neutral?
Date posted: August 5, 2019. Answers (1)