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This is the heat absorbed or evolved when one mole of any substance is formed from its constituent elements in their normal states
john3 answered the question on October 4, 2017 at 12:30
- Element M reacts with water at room temperature to produce 0.2 dm3 of gas. Determine the mass of M which was...(Solved)
Element M reacts with water at room temperature to produce 0.2 dm3 of gas. Determine the mass of M which was reacted with water. (Molar gas volume at room temperature is 24 dm3, Relative atomic mass of M = 7).
Date posted: October 4, 2017. Answers (1)
- A solution was made by dissolving 8.2g of calcium nitrate to give 2 litres of solution. (Ca = 40.0; N = 14.0;...(Solved)
A solution was made by dissolving 8.2g of calcium nitrate to give 2 litres of solution. (Ca = 40.0; N = 14.0; O = 16.0).
Determine the concentration of nitrate ions in moles per litre
Date posted: October 4, 2017. Answers (1)
- When 15cm3 of a gaseous hydrocarbon, P, was burnt in 100cm3 of oxygen, the resulting gaseous mixture occupied 70cm3 at room temperature and pressure....(Solved)
When 15cm^3 of a gaseous hydrocarbon, P, was burnt in 100cm^3 of oxygen, the resulting gaseous mixture occupied 70cm^3 at room temperature and pressure. When the gaseous mixture was passed through potassium hydroxide solution, its volume decreased to 25cm^3.
(a) What volume of oxygen was used during the reaction?
Date posted: October 4, 2017. Answers (1)
- Name one alloy of copper and state its use.
Alloy
Use(Solved)
Name one alloy of copper and state its use.
Alloy
Use
Date posted: October 4, 2017. Answers (1)
- Name two ores from which copper is extracted(Solved)
Name two ores from which copper is extracted
Date posted: October 4, 2017. Answers (1)
- A certain mass of gas occupies 146 dm^3 at 291 K and 98.31 kPa. What will be...(Solved)
A certain mass of gas occupies 146 dm^3 at 291 K and 98.31 kPa. What will be its temperature if its volume is reduced to 133 dm^3 at 101.325 kPa?
Date posted: October 4, 2017. Answers (1)
- A gas jar full gas V was opened in air. Explain the observation made by use of an equation.(Solved)
A gas jar full gas V was opened in air. Explain the observation made by use of an equation.
Date posted: October 3, 2017. Answers (1)
- what is evaporation?(Solved)
paper two.
Date posted: October 2, 2017. Answers (1)
- What is boiling?(Solved)
What is boiling?
Date posted: October 2, 2017. Answers (1)
- Define the term saturated solution(Solved)
What is a saturated solution?
Date posted: October 2, 2017. Answers (1)
- Give a reason why nitric (V) acid is stored in dark brown bottles.(Solved)
Give a reason why nitric (V) acid is stored in dark brown bottles.
Date posted: September 30, 2017. Answers (1)
- State one use of sodium carbonate(Solved)
State one use of sodium carbonate
Date posted: September 30, 2017. Answers (1)
- What is meant by the term dynamic equilibrium?(Solved)
What is meant by the term dynamic equilibrium?
Date posted: September 29, 2017. Answers (1)
- a) Name the following processes (i) When anhydrous calcium chloride was left in an open beaker
overnight a solution was formed.(ii) When sodium carbonate decahydrate crystals...(Solved)
a) Name the following processes:
i) When anhydrous calcium chloride was left in an open beaker
overnight a solution was formed.
ii) When sodium carbonate decahydrate crystals are left in an open beaker for some days it turned
into powder.
Date posted: September 29, 2017. Answers (1)
- What compounds form when hot concentrated sodium hydroxide is used instead of the cold
dilute sodium hydroxide.(Solved)
What compounds form when hot concentrated sodium hydroxide is used instead of the cold
dilute sodium hydroxide.
Date posted: September 29, 2017. Answers (1)
- Explain why the error in the Dalton's theory has not affected its validity?(Solved)
Explain why the error in the Dalton's theory has not affected its validity?
Date posted: September 29, 2017. Answers (1)
- Explain why a substance conducts electric current when in molten state and not in solid state.(Solved)
Explain why a substance conducts electric current when in molten state and not in solid state.
Date posted: September 28, 2017. Answers (1)
- A dry cell is used as a source of electric current.
State the role of manganese (IV) oxide mixed with carbon(Solved)
A dry cell is used as a source of electric current.
State the role of manganese (IV) oxide mixed with carbon
Date posted: September 28, 2017. Answers (1)
- During the extraction of zinc metal, the ore is crushed into powder and mixed with water and oil.
Air is also blown through the mixture.
i) What...(Solved)
During the extraction of zinc metal, the ore is crushed into powder and mixed with water and oil.
Air is also blown through the mixture.
i) What name is given to the process described above?
ii) The hull of a ship is made using Iron and blocks of zinc to prevent rusting. How does zinc
prevent the rusting of iron?
iii) Explain the process named in (i) above occurs.
Date posted: September 28, 2017. Answers (1)
- Fossil fuels are commonly used as sources of energy. Hydrogen gas is also a source of energy.
State and explain why hydrogen is a more attractive...(Solved)
Fossil fuels are commonly used as sources of energy. Hydrogen gas is also a source of energy.
State and explain why hydrogen is a more attractive fuel than the fossil fuels.
Date posted: September 28, 2017. Answers (1)