Chemical equation and chemical reactions

The bright magnesium ribbon changes into a white powder of ............... when it burns in air

• magnesium nitrite

• magnesium hydroxide

• magnesium oxide

• magnesium dioxide

On applying the law of constant ratios on the following reaction:

2Mg + O2 -----------------> 2MgO

we will find .................(knowing that Mg= 24 and O= 16)

• each 48 gm Mg combines with 32 gm O to form 80 gm MgO

• each 24 gm Mg combines with 16 gm O to form 40 gm MgO

• each 12 gm Mg combines with 8 gm O to form 20 gm MgO

• All the previous answers are correct

The .................... equation verifies the law of conservation of matter

• N2 + H2 ----------------> NH3

• NO + O2 ---------------> NO2

• KCl + AgNO3 ------------------> AgCl + KNO3

• H2O -----------------------> H2 + O2

In the molecule of CO2, the mass of C= 12 and O=16, so the mass of two molecules of Carbon dioxide equals ....... gm

• 22

• 44

• 88

• 33

The chemical reaction causes ...........

• breaking the bonds between the products and forming new bonds between the reactants

• the formation of bonds between the products, then breaking the bonds between the reactants

• breaking the bonds between the molecules of reactants and forming new bonds between the molecules of the products

• breaking the bonds between the products and reactants