Direct Combination Reaction

Which element is the most active from the choices below?

• Potassium

• Gold

• Calcium

• Lead

.................... elements are the most stable elements.

• Metals

• Nonmetals

• Noble gases

• Metalloids

In ammonia molecule ( NH₃ ) , the number 3 refers to the number of .........................

• N and H atoms in one molecule

• H atom in one molecule

• N atom in one molecule

• the valency of hydrogen

When an acid dissolves in water, it produce .............ions.

• (OH)^-

• H^-

• H⁺

• (OH)⁺

All of these substances turn litmus paper into red except ...................

• HCl

• NaOH

• HNO₃

• H₂SO₄

Mona bought a cup of yogurt and found the taste is sour, so she concluded that it contains a compound from ...................

• acids

• bases

• salts

• oxides

The sum of reactants masses in any chemical reaction is .................... the sum of products masses.

• doubled

• more than

• equal to

• less than

Direct combination reaction takes place between ....................

• two nonmetals

• a metal and a nonmetal

• a compound with another

• all of the previous answers

Which of the following is considered a balanced chemical equation?

• Mg + O₂ -----> MgO

• 2 Mg + O₂ -----> MgO

• Mg + O₂ ----->2 MgO

• 2 Mg + O₂ ----->2 MgO

Choose the suitable diagram for a monovalent metallic element.

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