Which of the following elements
will not react when exposed to hot water vapor? (A) Zinc, (B) potassium, (C)
calcium, (D) copper, (E) iron.
To answer this question, we need to
determine which of the given elements will not react with hot water vapor.
All of the given elements are
metals. Some metals are more reactive than
others. The chemical activity series is a
list that shows how active elements are when compared to others. We can use this list to help us
determine which elements will react with water.
Here we have a list of the names
and chemical symbols of some metal elements and the nonmetal element hydrogen. Elements that are higher up on the
series are more active than elements that are lower down. Elements that are above the element
hydrogen can react with water. But we need to know which elements
will not react with hot water vapor. So let’s take a look at the
elements in the series more closely.
Metals that are higher on the
series react faster and more strongly with water. For example, potassium and sodium
react very quickly and intensely with cold water. If we added a piece of potassium to
water, we would observe a lot of bubbling and may see flames on the surface of the
water. The bubbling happens because
hydrogen gas is being produced during the chemical reaction. The reaction also releases a lot of
heat. Because of this, some of the
hydrogen gas can ignite. This is one reason why we see
Calcium and magnesium are below
sodium and potassium in the series. These two metals react more slowly
with cold water. They also react less strongly. If we added these metals to water,
we would still see bubbling as the hydrogen gas is produced. But we would not see any
Zinc and iron are even less active
than calcium and magnesium. These two metals do not react with
cold water. So does this mean they do not react
with water vapor? These metals are active enough to
react with water vapor, but only if the water vapor is very hot.
To do this, we could strongly heat
a test tube that contains cotton wool soaked with water and zinc metal. The water is converted to steam and
reacts with zinc. Yellowish zinc oxide and hydrogen
gas form, which escapes the tube.
The elements copper and silver are
less active than hydrogen. They do not react with water at
all. This means they will not react with
liquid water or water vapor.
Now we see that answer choices (A),
(B), (C), and (E) are all incorrect. These four metals are more active
than hydrogen and can react with water. Copper is the only element in the
answer choices that is not active enough to react with hot water vapor. So the correct answer is answer
choice (D), copper.