Chemistry Concepts: Density & Reactions

Questions and Answers

What is the density of the metal if a graduated cylinder contains 20.6ml of water, and after placing the metal, the volume is 23.7ml, and the mass of the metal is 34.17g?

11 g/ml

Convert 45.90cm into meters.

0.4590 m

What was the purpose of the manganese dioxide (MnO2) in experiment 3?

To act as a catalyst and speed up the decomposition of hydrogen peroxide.

Why were the bottles of oxygen stored with the mouth up in experiment 3?

To help trap oxygen as it is more dense and floats to the top. Signup and view all the answers

Why did the candle burn longer in a bottle of oxygen compared to a bottle of air?

Because oxygen supports combustion better than air. Signup and view all the answers

What is AgNO3?

Silver Nitrate Signup and view all the answers

What is HI(aq) commonly known as?

Hydroiodic acid Signup and view all the answers

What is the formula for Copper (II) Bromide?

CuBr2 Signup and view all the answers

What is the formula for Aluminum oxide?

Al2O3 Signup and view all the answers

What is the formula for lead (II) fluoride?

PbF2 Signup and view all the answers

What is the formula for chromium (III) phosphide?

ChP Signup and view all the answers

What evidence indicated that the liquid obtained from copper (II) sulfate pentahydrate was water?

Cobalt chloride paper turned white and anhydrous copper(II) sulfate turned blue. Signup and view all the answers

What evidence of a chemical reaction was observed when the anhydrous salt samples were treated with the liquid from the hydrate?

Change in temperature and color from white to blue. Signup and view all the answers

Could the decrease in mass of the unknown upon heating be due to loss of other substances?

Yes, due to decomposition of the heated salt. Signup and view all the answers

If a hydrated salt sample with initial mass of 4.8702g decreased to 3.0662g, what is the minimum mass after reheating?

3.0162g Signup and view all the answers

What was the percent water in the original hydrated sample if the mass lost was 1.8053g?

37.07% Signup and view all the answers

Why did coarse salt take longer to dissolve than fine salt?

Coarse salt consists of larger crystals. Signup and view all the answers

How does temperature affect the rate of dissolving salt?

Hot temperatures dissolve salt faster. Signup and view all the answers

What is a solution called if it dissolved completely?

Unsaturated Signup and view all the answers

What is a solution called if it does not dissolve completely?

Saturated Signup and view all the answers

What is the percentage by mass of NaCl in a saturated solution at 50C?

27.0% NaCl Signup and view all the answers

What is the solubility of potassium bromide at 23C?

66.8g KBr Signup and view all the answers

How much additional barium chloride can be dissolved by heating a saturated solution from 30C to 60C?

12.6g BaCl2 Signup and view all the answers

How many grams of solute are dissolved in 100g of water in a saturated solution of KCl at 50C?

42.6g KCl Signup and view all the answers

What is the total mass of the KCl solution at 50C if 42.6g of solute is dissolved?

142.6g Signup and view all the answers

What is the mass percent of a KCl solution at 50C?

29.9% Signup and view all the answers

If the KCl solution is heated to 100C, how much more KCl can be dissolved?

13.0g KCl Signup and view all the answers

What caused double displacement reactions to occur in the experiment?

Gas, Precipitate, and Slightly ionized compound. Signup and view all the answers

Write the equation for the decomposition of sulfurous acid.

H2SO3 ===> H2O + SO2 Signup and view all the answers

Arrange Pb, Mg, and Zn in order of their activities, listing the most active first.

Mg, Zn, Pb Signup and view all the answers

Arrange Cu, Ag, and Zn in order of their activities, listing the most active first.

Zn, Cu, Ag Signup and view all the answers

Arrange Mg, H, Ag in order of their activities, listing the most active first.

Mg, H, Ag Signup and view all the answers

Arrange the following metals: Mg, Zn, Pb, Cu, Ag in order of their activities, listing the most active first.

Mg, Zn, Pb, Cu, Ag Signup and view all the answers

Why can't the position of hydrogen be fixed exactly in the activity series?

Hydrogen's activity varies depending on the element it's being compared to. Signup and view all the answers

What additional tests would be needed to establish the exact position of hydrogen in the activity series?

Test the reactivity of hydrogen compared to Mg, Zn, and Ag. Signup and view all the answers

Would silver react with dilute sulfuric acid? Why or why not?

No, because silver is less active than hydrogen. Signup and view all the answers

Would magnesium react with dilute sulfuric acid? Why or why not?

Yes, because magnesium is more active than hydrogen. Signup and view all the answers

If 50ml of water were added to a sample of KHP instead of 30ml, would the titration require more, less, or the same amount of base?

The same amount of base. Signup and view all the answers

How many moles are represented in 1.106g of KHP?

0.005416 mol Signup and view all the answers

How many moles of NaOH are in 18.38ml of 0.1574 M NaOH solution?

0.002893 mol Signup and view all the answers

What is the molarity of the base if a student used 1.276g of KHP that requires 19.84 mL of base?

0.3149 M Signup and view all the answers

If Freddy needed to calculate the mass of his KHP sample, what was the calculated mass if his titration required 18.46 mL of base at 0.2987 M?

1.126g Signup and view all the answers

What mass of solid NaOH is needed to make 645ml of Freddy's NaOH solution?

7.71g Signup and view all the answers

Study Notes

Density Calculation

Density of metal calculated by dividing mass by the volume of displaced water.
Displaced volume: 23.7ml - 20.6ml = 3.1ml.
Density result: 34.17g / 3.1ml = 11g/ml.

Unit Conversion

To convert from centimeters to meters: divide by 100.
Example: 45.90cm = 0.4590m.

Role of Manganese Dioxide

Manganese dioxide (MnO2) acts as a catalyst in the decomposition of hydrogen peroxide.
It accelerates the production of oxygen gas from the reaction.

Oxygen Storage

Bottles containing oxygen gas are stored upright to utilize the gas's higher density.
This position aids in trapping oxygen effectively.

Candle Burning Experiment

A candle burns longer in oxygen than in air due to higher oxygen levels supporting combustion.
Combustion is significantly more efficient in oxygen-rich environments.

Chemical Formulas

AgNO3: Silver Nitrate.
HI(aq): Hydroiodic acid.
CuBr2: Copper (II) Bromide.
Al2O3: Aluminum oxide.
PbF2: Lead (II) fluoride.
ChP: Chromium (III) phosphide.

Evidence of Water Formation

Cobalt chloride paper turning white indicates the presence of water.
When anhydrous copper(II) sulfate mixes with obtained liquid, it turns blue, confirming water formation.

Chemical Reaction Evidence

Physical changes like heating and steam production indicate a chemical reaction occurred with anhydrous salts.

Mass Loss Upon Heating

Decomposition of salts when heated can also lead to mass loss and color change.

Minimum Mass After Heating

After cooling, minimum mass of a heated sample is calculated by subtracting potential error (0.05g).

Percent Water in Hydrated Sample

Percent calculation: (mass lost / initial mass) x 100% results in 37.07% water content in the original sample.

Dissolving Rates

Fine salt dissolves faster than coarse salt due to greater surface area exposure in a solvent.

Solubility Calculations

For NaCl in saturated solution at 50°C: (37g NaCl/Total weight) x 100 = 27.0% by mass.
Potassium bromide solubility estimation involves average changes across temperature range calculations.

Additional Soluble Capacity

Heating a saturated solution can dissolve additional quantities of solute, e.g., 12.6g of BaCl2 at increased temperatures.

Saturation and Percent Mass

Total mass of a KCl solution at saturation is the sum of solute and solvent weights.
Mass percent calculation at 50°C gives 29.9% for KCl solutions.

Activity Series of Metals

Relative activities ordered: Mg > Zn > Pb; Zn > Cu > Ag; Mg > H > Ag.
Hydrogen's position relative to metals varies based on experimental conditions due to reactivity levels.

Reactivity with Acids

Silver does not react with dilute sulfuric acid; it is less active than hydrogen.
Magnesium reacts with dilute sulfuric acid as it is more active than hydrogen and will replace it.

Titration Calculations

Titration data allows calculation of molarity and masses of compounds involved, for example, using KHP and NaOH.
Calculate moles of NaOH based on volume and concentration for titration results.

Final Weight Considerations

The mass of NaOH needed correlates with the created solution's concentration and volume requirements, leading to precise mass calculations for experiments.

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Description

Explore key chemistry concepts including density calculation, unit conversion, and the role of manganese dioxide as a catalyst. The quiz covers practical applications like oxygen storage and the effects on combustion in various environments.