An 18-karat gold necklace is 75% gold by mass, 16% silver, and 9.0% copper.A. What is the mass, in grams, of the necklace if it contains 0.24 Oz of silver?
B. How many grams of copper are in the necklace.?
C. If the 18- karat gold has a density of 15.5g/cm^3, what is the volume in cubic centimeters?

The percentage yield of the reaction if 23.1 grams of FeCl₃ is created by 10.61g of Fe is 74.9 %.

What is percent yield?

Percent yield of a reaction is the ratio of actual yield to the theoretical yield multiplied by 100.

As per the given balanced reaction, one mole or 55.85 g of Fe is needed to produce 1 mole or 162.2 g of FeCl₃.

Then theoretically, the mass of FeCl₃ which can be produced by 10.61 g of Fe is calculated as follows:

= (10.61 × 162.2) / 55.85

=30.81 g

This is the theoretical yield.

The actual yield is given 23.1. Now the percentage yield is calculated as follows:

Percentage yield = (Actual yield/ heretical yield)×100

                             = (23.1/30.81)×100

                             = 74.9 %.

Hence, the percentage yield of the reaction is 74.9 %.

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Pb(NO₃)₂ ⇒limiting reactant

moles PbI₂ = 1.36 x 10⁻³

% yield  = 87.72%

Further explanation

Given

Reaction(unbalanced)

Pb(NO₃)₂(s) + NaI(aq) → PbI₂(s) + NaNO₃(aq)

Required

• moles of PbI₂
• Limiting reactant
• % yield

Solution

Balanced equation :

Pb(NO₃)₂(s) + 2NaI(aq) → PbI₂(s) + 2NaNO₃(aq)

mol Pb(NO₃)₂ :

= 0.45 : 331 g/mol

= 1.36 x 10⁻³

mol NaI :

= 250 ml x 0.25 M

= 0.0625

Limiting reactant (mol : coefficient)

Pb(NO₃)₂ : 1.36 x 10⁻³ : 1 = 1.36 x 10⁻³

NaI : 0.0625 : 2 = 0.03125

Pb(NO₃)₂ ⇒limiting reactant(smaller ratio)

moles PbI₂ = moles Pb(NO₃)₂ = 1.36 x 10⁻³(mol ratio 1 : 1)

Mass of PbI₂ :

= mol x MW

=  1.36 x 10⁻³ x 461,01 g/mol

= 0.627 g

% yield = 0.55/0.627 x 100% = 87.72%

Final answer:

A chemical change or reaction between elements or compounds may occur when there is enough energy present. This can be in the form of heat, light, or electricity. An example of this is the reaction between hydrogen and oxygen to form water, which requires a spark.

Explanation:

If two or more elements or chemical compounds come into contact with one another and there is enough energy present, a chemical change may take place. This is because a chemical reaction, which represents a chemical change, requires energy to break the bonds of the reactants and form new bonds in the products. This energy can be in various forms such as heat, light, or electricity.

For example, the reaction between hydrogen and oxygen to form water is a chemical change that requires energy in the form of a spark. On the other hand, an exothermic reaction, such as the combustion of gasoline, releases energy in the form of heat and light.

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Answer:

energy

Explanation:

"If two or more elements or chemical compounds come into contact with one another and there is enough energy present, a chemical change may take place." this was on a science lesson, it's correct.

Explanation

• Number of moles of chloride ions in the final solution:

• Each mole of barium chloride contains two moles of chloride ions. Thus the concentration of chloride ions in the initial 1.51 M barium chloride solution:

Therefore