| decomposition reaction- define. | reactions in which a single compound is broken down into multiple products by the action of a catalyst. |
| decomposition reaction- define. | reactions in which a single compound is broken down into multiple products by the action of a catalyst. |
| decomposition reaction- define. | reactions in which a single compound is broken down into multiple products by the action of a catalyst. |
| decomposition reaction- define. | reactions in which a single compound is broken down into multiple products by the action of a catalyst. |
| decomposition reaction- define. | reactions in which a single compound is broken down into multiple products by the action of a catalyst. |
| decomposition reaction- define. | reactions in which a single compound is broken down into multiple products by the action of a catalyst. |
| decomposition reaction- define. | reactions in which a single compound is broken down into multiple products by the action of a catalyst. |
| decomposition reaction- define. | reactions in which a single compound is broken down into multiple products by the action of a catalyst. |
| decomposition reaction- define. | reactions in which a single compound is broken down into multiple products by the action of a catalyst. |
| decomposition reaction- define. | reactions in which a single compound is broken down into multiple products by the action of a catalyst. |
| what is a chemical reaction? | when the chemical structure of a substance changes to bring about a new substance it is said to have gone through a chemical reaction. such as digestion of food, respiration and burning of natural gas. |
| Why do we have to clean a magnesium ribbon? | magnesium is a reactive metal so if it is exposed to atmospheric air for a long time it will react with the oxygen to produce a layer of magnesium oxide which will prevent further oxidation. sanding it will remove that layer. |
| what colour does a magnesium ribbon burn with? | Dazzling white flame |
| what is produced after burning it? | powdered white ash. Mg+O2------>MgO. |
| what is the nature of magnesium hydroxide? | basic in nature. since it is a metallic oxide. on dissolving in water it will produce a base- magnesium hydroxide. |
| write the lead nitrate and potassium iodide reaction. | Pb(NO3)2+KI-------->PbI+KNO3. pbi is a white precipitate. this is a double displacement and precipitation reaction. |
| reaction of zinc granules and sulfuric acid | acid on reacting with metal gives a salt and hydrogen gas. this is a double displacement reaction. this is an exothermic reaction. |
| what is a chemical equation? | symbolic representation of a chemical reaction using formulae and signs (an physical states, pressure, temperature) is a chemical equation. |
| balance- C6H12O6 + O2 → CO2 + H2O | C6H12O6 + 6O2 → 6CO2 + 6H2O |
| Al + O2 → Al2O3 | 4Al + 3O2 → 2Al2O3 |
| N2 + H2 → NH3 | N2 + 3H2 → 2NH3 |
| FeCl3 + NaOH → NaCl + Fe(OH)3 | FeCl3 +3 NaOH → NaCl + Fe(OH)3 |
| Zn + HCl → ZnCl2 + H2 | Zn +2 HCl → ZnCl2 + H2 |
| P2O5 + H2O → H3PO4 | P2O5 + 3 H2O → 2 H3PO4 |
| translate- Hydrogen gas combines with nitrogen to form ammonia. | N2(g) + 3H2(g) ------> 2NH3(g) |
| Hydrogen sulphide gas burns in air to give water and sulphur dioxide. | 2H2S + 3O2 → 2SO2 + 2H2O |
| Barium chloride reacts with aluminium sulphate to give aluminium chloride and a precipitate of barium sulphate. | 3BaCl2(aq)+Al2(SO4)3(aq)→2AlCl3(aq)+3BaSO4(s) |
| Potassium metal reacts with water to give potassium hydroxide and hydrogen gas. | 2K(s)+2H2O(l)→2KOH(aq)+H2(g) |
| what is a balanced chemical equation? | when the number of atoms of particular elements on the reactant side is equal to the number of that element in the product side it is said to be balanced. |
| why is it necessary to balance the equation? | so that it follows the law of conservation of mass. it ststes that mass can neither be created nor be destroyed. |
| what is an unbalanced chemical equation called? | skeletal equation |
| when is aq written? | when the reactant or product exists as a solution in water. |
| what can we ad to the equation to make it more informative? | physical nature of the reactant or product- s, l, g, aq. the pressure, the temperature, the catalyst such as heat, light or electricity. |
| CO+H2 gives | CH3OH-----methanol |
| how can we know that a chemical reaction has taken place? | 1. change in state
CO(g)+H2(g)------>CH3OH(l)
2. change in colour
Fe(s)+CuSO4(aq)------->FeSO4(aq)+Cu(s). blue coloured solution changes to a green coloured one.
3. change in temperature
heat can be given out as a process. they are exothermic reactions and increase the surrounding temperature. such as Zn+H2SO4------>ZnSO4+H2.
heat can be taken in as a catalyst. this is an endothermic reaction. surrounding temperature reduces. such as CaCO3------CaO+Co2
4. evolution of gas. Zn+H2SO4------>ZnSO4+H2. hygrogen is in gaseous state.
5. formation of precipitate. such as Pb(NO3)2+KI-------->PbI+KNO3. pbi is a white precipitate. this is a double displacement and precipitation reaction. any reaction which gives a precipitate is a precipitation reaction. |
| define combination reaction. | reactions in which two or more elements or compounds react to form a single product. they are generally exothermic in nature. such as
burning of natural gas- CH4------>CO2+H2O+heat
respiration- C6H12O6+6O2------6H2o+6Co2+energy. this energy helps in maintaining body temperature.
decomposition of organic matter.
CaO+h2O----->Ca(OH)2. highly exothermic. applied to walls which react with co2 to produce caco3 which gives a shiny finish. slow reaction.
are also known as synthesis reactions and are endothermic in nature |
| decomposition reaction- define. | reactions in which a single compound is broken down into multiple products by the action of a catalyst. if the catalyst is heat the it is thermal decomposition
Pb(NO3)2------>PbO+NO2+O2
FeSO4.5H2O------>Fe2O3+SO2+SO3 burning smell of sulphur.
if the catalyst is light then it is calle photolystic decomposition.
2AgCl------>2Ag+Cl2. 2AgBr------>2Ag+Br2. these are used in black and white photography. the cl and br turn into gas leaving behind grey Ag. the br is reddish brown. agbr is pale yellow
when the catalyst is electricity. it is known as electrolytic decompostion
2H2O-------2H2+O2
h2 is produced in the cathode and oxygen in the anode. twice the volume of oxygen is produced.
are generally endothermic in nature |
| displacement reaction- define | reactions in which a more reactive element displaces a lesser reactive element. such as Fe+CuSO4------->FeSO4+Cu
Pb+CuCl2------->PbCl2+Cu
only one reaction happens |
| define - double displacement reactions | reactions in which ions switch places. 2 displacements happen.
such as Na2SO4+Bacl2---->BaSO4+NaCl. baso4 is a white ppt |
| what is oxidation | addition of oxygen,loss of hydrogen or electrons is oxiation such as C+o2---->CO2 |
| what is reduction? | addition of hydrogen removal of oxygen or electrons. such as
CUo+h2----->Cu+H2O |
| what are redox reactions? | reactions in which oxidation and reduction reactions happen simultaneously. such as CuO+h2----->Cu+H2O |
| what are oxidising agents? | substances which oxidise another substance. fluorine is the strongest oxiising agent. such as in CuO+h2----->Cu+H2O, CuO is the oxidising agent. |
| what are reducing agents? | substances which reduce another substance. lithium is the strongest reducing agent.
such as in CuO+h2----->Cu+H2O, H2 is the reducing agent. |
| what is corrosion? | Corrosion definition states that it is a natural process that causes the transformation of pure metals into undesirable substances when they react with substances such as water or air. This reaction causes damage or disintegration of metal as it interfaces with the environment and gradually spreads to the entire bulk of the metal.
metals are painted to stop its exposure to atmosphere to slow down corrosion. |
| are all metals corroded easily? | no, metals which are placed high in the reactivity series quickly but the ones which are placed down such as gold and silver take a lot of time to tarnish. aluminium does not corrode like other metals because a layer of aluminium oxide forms on the layer of aluminium which prevents further oxidation. |
| what is rancidity? | when foods containing fats and oils are exposed to atmospheric air they react to get oxidised and their smell and taste changes thus they turn rancid. |
| oil and fat containing foods are packed with nitrogen. Why? | nitrogen is a non reactive element so they o not react with the foo to turn rancid. |
| what can be added to food to reduce the rate of rancidity? | antioxidants |
| how can silver be refined? | Al+AgNO3------>Al(NO3)3+Ag---------displacement reaction |
| what products does their reaction yield Ba(OH)2+NH4Cl | BaCL2+Nh3+H2O |
