CHEMICAL REACTIONS AND EQUATIONS

CHAPTER 1

why does a magnesium ribbon need to be rubbed with sandpaper before burning it?

magnesium is a reactive metal, hence it reacts with oxygen in air to form a layer of magnesium oxide around it. this prevents it from burning. Hence, it should be cleaned first.

what is a skeletal chemical equation?

an equation in which the total mass of reactants is not equal to the total mass of products, hence the equation is not balanced, is called skeletal chemical equation.

what is the law of conservation of mass?

it states that mass can neither be created nor destroyed in a chemical reaction. That is, the total mass on the products side and the reactants side has to be equal.

what is the color of MgO?

White powder

what is the name and color of the precipitate formed when lead nitrate reacts with potassium iodide?

The precipitate formed is lead iodide, which is yellow in color.

what is the method to balance chemical equations by making trials called?

the HIT and TRIAL method

How to make a chemical equation more informative?

the physical states of the reactants and products should be mentioned along with their name and formulae. the states can be mentioned as solid (s), liquid (l), gaseous (g), and aqueous (aq). additionally, a precipitate can be mentioned with its color as a (↓) arrow. other conditions such as catalyst, temperature, pressure are also mentioned above the arrow.

combination reactions are always___, and decomposition reactions are always_______.

exothermic, endothermic

calcium carbonate is formed by the reaction of____________?

slaked lime and carbon-di-oxide.

decomposition of vegetable matter is____________ reaction?

exothermic

respiration is a ____ reaction?

exothermic

what is the color of ferrous sulphate crystals?

GREEN

______ is used in the manufacturing of cement.

CaO

what is the name and color of precipitate formed in the reaction of sodium sulphate and barium chloride?

The precipitate formed is called barium sulphate, and it is a white solid.

what is the color of copper oxide?

The color of copper oxide is black.

what is an oxidation reaction?

An oxidation reaction is a chemical process in which a substance gains oxygens or loses hydrogen in a chemical reaction.

what is corrosion?

when a metal is exposed to surroundings, and is therefore attacked by various gases, moisture etc, it is said to corrode. this process is called corrosion.

what is rancidity?

when fats and oil are exposed to the environment and react with oxygen, they become rancid, and their smell and taste change. this process is called rancidity.