Purity Flashcards
What is a pure element?
A pure element consists of only one type of atom, and every atom is exactly the same.
Example: Pure gold is made entirely of gold atoms.
What is an alloy?
An alloy is a mixture of metals.
Example: Gold alloys can include metals like copper or silver.
How is gold purity measured?
Gold is marked in carats, indicating its purity. Pure gold = 24 carats.
Example: 18-carat gold contains 18 parts of gold out of 24 parts, with the rest being other metals.
Purity calculation: \frac{18}{24} \times 100 = 75\%
What do the carat numbers tell you about gold?
Lower carats (e.g., 8 or 14 carats) contain more other metals, making the gold less pure. Higher carats (e.g., 24 carats) are closer to pure gold.
How is silver purity marked?
Silver is marked with the number of pure parts per thousand.
Example: Silver 925 means it has 925 parts silver and 75 parts other metals out of 1000 parts.
Purity calculation: \frac{925}{1000} \times 100 = 92.5\%
What is the difference between Silver 925 and Silver 900?
Silver 925 has 92.5% purity. Silver 900 has only 90% purity, meaning it contains more other metals.
How does the appearance of gold change with purity?
As gold purity decreases (e.g., 8, 14, or 18 carats), the color changes from yellow-gold to slightly coppery.
What are diamonds made of?
Diamonds are made from the element carbon.
The carbon atoms are arranged in a specific structure.
What are pure diamonds like?
Pure diamonds contain only carbon atoms.
They are colorless and translucent (let light through).
How do impurities affect diamond color?
If other elements mix with carbon atoms, diamonds change color:
- Yellow diamond: A few carbon atoms are replaced by nitrogen.
- Blue diamond: Some carbon atoms are replaced by boron.
- Green diamond: Formed when one atom per 1000 carbon atoms is replaced by nitrogen, nickel, or hydrogen.
Green diamonds are the rarest.
What percentage of 9-carat gold is pure gold?
9-carat gold contains 37.5% pure gold.
Calculation: \frac{9}{24} \times 100 = 37.5\%
What percentage of silver is in silver marked 900?
Silver marked 900 contains 90% pure silver.
Calculation: \frac{900}{1000} \times 100 = 90\%
Which element makes diamonds blue?
Boron mixed with carbon makes diamonds blue.
Which elements may cause a diamond to be green?
Nitrogen, nickel, or hydrogen can cause a diamond to be green.
What is seawater made of?
Seawater consists of water and various salts like sodium chloride.
96.5% is water, and 3.5% is salt.
How is sodium chloride obtained from seawater?
By letting seawater evaporate in shallow areas (salt beds) using the Sun’s heat.
Pure sodium chloride must be separated from other salts dissolved in seawater.
What salts are found in seawater?
Seawater salts include:
- Sodium chloride (68% of salts)
- Magnesium chloride (14.6%)
- Sodium sulfate (11.4%)
- Calcium chloride (3.1%)
- Other salts (2.9%)
What is the percentage of sodium chloride in seawater?
Sodium chloride makes up 68% of the salts in seawater.
Example: In 1000 g of seawater:
- 35 g salts × 0.68 = 23.8 g sodium chloride.
What are salts made from?
Salts are compounds formed from acids.
Example:
- Sodium chloride is formed from hydrochloric acid.
- Sodium sulfate is formed from sulfuric acid.
How much magnesium chloride is in 1000 g of seawater?
Magnesium chloride is 14.6% of salts.
Calculation:
- 35 g salts × 0.146 = 5.11 g magnesium chloride.
Why is it important for products to be pure in chemical reactions?
Purity ensures there are no impurities that could affect the product’s function.
Example: Medicines must be pure to avoid harming the patient or reducing effectiveness.
What happens in a simple reaction?
A simple reaction produces only one product.
Example reaction: Magnesium + Oxygen → Magnesium oxide.
What is magnesium oxide?
Magnesium oxide is the product of magnesium reacting with oxygen.
What happens in reactions with more than one product?
The products are mixed together and must be separated and purified to obtain the desired pure product. Some reactants might remain unused and mix with the products.
Example of a reaction with multiple products: Silver nitrate + Sodium chloride
Reactants: Silver nitrate + Sodium chloride
Products: Sodium nitrate + Silver chloride
Example of a reaction: Sulfuric acid + Sodium hydroxide
Reactants: Sulfuric acid + Sodium hydroxide
Products: Sodium sulfate + Water
Example of a reaction: Barium chloride + Sodium sulfate
Reactants: Barium chloride + Sodium sulfate
Products: Barium sulfate + Sodium chloride
Example of a reaction: Lead nitrate + Potassium iodide
Reactants: Lead nitrate + Potassium iodide
Products: Potassium nitrate + Lead iodide
Example of a reaction: Copper carbonate + Hydrochloric acid
Reactants: Copper carbonate + Hydrochloric acid
Products: Copper chloride + Water + Carbon dioxide
