CHEMICAL REACTIONS AND EQUATIONS - SANTHOSH G S STR GJC SIRA

A product named as ‘X’ obtained when a small piece of

magnesium ribbon is burnt in air. Then the ‘X’ is

• Magnesium oxide

• Magnesium carbonate

• Magnesium chloride

• Magnesium bicarbonate

One of the following observations helps us to determine

the chemical reaction takes place is

• Change in shape

• Change in temperature

• Change in colour

• Both a and b

Complete.     $A\ \ +\ \ \ B\ \ \ \ \ \ \rightarrow\ \ \ \ \ \$   $MgO$  . Here A and B are                                  
                     

•    $\ Mg\ and\ CO_2$  

•    $Mg_2\ and\ O_2$  

•    $Mg\ and\ O_2$  

•   $Mg\ and\ O_3$  

Identify the correct and balanced chemical equation.

•   $4Fe\ \ +\ \ 2H_2O$    $\rightarrow$    $Fe_3O_4\ \ \ +\ \ 2H_2$  

•   $3Fe\ \ +\ \ 4H_2O$     $\rightarrow$   $Fe_3O_{4\ \ \ }+\ \ \ 4H_2$  

•   $4Fe\ \ \ +\ \ \ 4H_2O$    $\rightarrow$   $4Fe_3O_{4\ \ \ }+\ \ \ 4H_2$  

•    $3Fe\ \ \ +\ \ \ 4H_2O$    $\rightarrow$   $4Fe_3O_{4\ \ \ }+\ \ \ 4H_2$  

Chemical combination reaction is one in which

• One reactant chemically decompose to form two or more products

• Exchange of ions between the atoms takes place

• One element of compound displaces another element of another compound

• Two or more reactants chemically combine together to form only one reactant

Burning of magnesium ribbon in presence of air is an example for

• Chemical combination

• Chemical decomposition

• Chemical displacement

• Chemical double displacement

Calcium oxide reacts vigorously with water to produce

•   $CaCO_{3\ }\ \ \rightarrow\ \ \ CaO\ \ \ +\ \ \ CO_2$  + Heat released

•   $\ C$  + $O_2$ $\rightarrow$ $CO_2$ + Heat absorbed

•   $CaO$  + $H_2O$ $\rightarrow$ $Ca\left(OH\right)_2$ + Heat liberated

•   $2CaO$  + $CO_2$ $\rightarrow$ $2CaCO_3$ + Heat absorbed

Exothermic reaction among the following.

i) Burning of coal

ii) Respiration in animals

iii) Reaction between calcium and water

iv) Decomposition of vegetable matter into compost

• ii and iv only

• i, ii and iii only

• i, iii and iv only

• i, ii, iii and iv only

The chemical name of quick lime or lime is

• Calcium hydroxide

• Calcium oxide

• Calcium carbonate

• Calcium bicarbonate

Chemical combination reaction is opposite to chemical

decomposition reaction. This is because

• One product is formed in both the reactions

• Two reactants are participating in both the reactions

• Two reactants react to form only one product in combination

  reaction

• Two reactants decompose to form only one product in

  decomposition reaction