Question

What are Alloys? Write down the composition of any three
Alloys.

Write down four methods to detect the chemical reactions.

What is the function of the pH scale? Write down its range.

What is a neutralization reaction? Write down its word equation
and any two uses.

Write down the word equations for:

A.Potassium Carbonate + Nitric acid

B. Zinc Carbonate + sulfuric acid

Explain what are the causes of rusting and how can we reduce
the risk of rusting?

Answer 1

Answer:

1. An alloy is a combination of a metal with at least one other metal or nonmetal. The combination must be part of a solid solution, a compound, or a mixture with another metal or nonmetal in order for it to be considered an alloy.

(A) Stainless steel: Iron, Chromium (18%), nickel (5%)

(B) Brass - 80% copper 20% zinc

(C)  Bronze - 90%copper 10%tin

2. Methods to detect chemical reactions are:

a. Change in color of products.

b. Evolution of smell or odor.

c. Evolution of heat while the reaction is happening.

d. Precipitation of products after the reaction is held.

3. The pH scale measures how acidic or basic a substance is. The pH scale ranges from 0 to 14. A pH of 7 is neutral. A pH less than 7 is acidic.

4. A chemical reaction between an acid and a base is known as Neutralization Reaction.

a. HBr(acid) +KOH(base)→KBr(salt) +H2O(water)

b.HCl(acid)+NaOH(base)→NaCl(salt)+H2O(water)

5.

a. $K_{2}C0_{3} (aq) + 2HNO_{3} (aq)$→$2KNO_{3} (aq) + H_{2} 0(1) + CO_{2} (g)$

b. $H_{2} SO_{4} (aq) + Zn(OH)_{2} (aq)$→$Zn(SO)_{4} (aq) + 2H_{2}O(l)$

6. Rusting is caused by the oxidization of the iron in the steel creating iron oxide. This is generally caused when moisture and oxygen are present.

There are several ways to prevent oxidization:

a. Pickling - place the steel or iron in oil and keep it well coated. This method is often used for firearms and works by keeping the moisture out of the steel.

b. Coating- using a paint product to coat the steel keeps both moisture and oxygen from attacking the steel. Complete coverage is important to keep the steel from rusting

c. Galvanizing or zinc coatings - These methods utilize cathodic protection or a “sacrificial metal” to protect the steel. The zinc is attacked before the oxygen begins to work on the steel the prolonging and preserving the steel during the oxidization process.

d. Materials selection - The use of high-grade stainless steel is another alternative. While expensive stainless does not generally rust as easily as steel or iron and thus is widely used for marine applications where conditions for rusting are ideal.

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