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Sever21 [200]
4 years ago
7

A jar containing only nickels and dimes contains a total of 60 coins. the value of all the coins in the jar is $4.45. solve by e

limination to find the amount of nickels and dimes that are in the jar.
Chemistry
1 answer:
weqwewe [10]4 years ago
7 0
1 nickle = 5 cents

1 dime = 10 cents

$4.45 = 445 cents

let

n = the number of nickles, n>=0

d = the number of dimes, d>=0

a jar containing only nickels and dimes contain a total of 60 coins:

n + d = 60

the value of all the coins in the jar is $4.45:

5n + 10d = 445

by solving the system of equations:

n + d = 60

5n + 10d = 445

we find:

n = 31 nickels

d = 29 dimes
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During a combustion reaction, 9.00 grams of oxygen reacted with 3.00 grams of CH4.
Monica [59]

Answer:

0.74 grams of methane

Explanation:

The balanced equation of the combustion reaction of methane with oxygen is:

  • CH₄ + 2 O₂ → CO₂ + 2 H₂O

it is clear that 1 mol of CH₄ reacts with 2 mol of O₂.

firstly, we need to calculate the number of moles of both

for CH₄:

number of moles = mass / molar mass = (3.00 g) /  (16.00 g/mol) = 0.1875 mol.

for O₂:

number of moles = mass / molar mass = (9.00 g) /  (32.00 g/mol) = 0.2812 mol.

  • it is clear that O₂ is the limiting reactant and methane will leftover.

using cross multiplication

1 mol of  CH₄ needs → 2 mol of O₂

???  mol of  CH₄  needs → 0.2812 mol of O₂

∴ the number of mol of CH₄ needed = (0.2812 * 1) / 2 = 0.1406 mol

so 0.14 mol will react and the remaining CH₄

mol of CH₄ left over = 0.1875 -0.1406 = 0.0469 mol

now we convert moles into grams

mass of CH₄ left over = no. of mol of CH₄ left over *  molar mass

                                    = 0.0469 mol * 16 g/mol = 0.7504 g

So, the right choice is 0.74 grams of methane

3 0
3 years ago
The mechanism for producing a concentrated urine involves all of the following except
avanturin [10]

Answer:

The correct answer is "obligatory water reabsorption in the proximal convoluted tubule".

Explanation:

The mechanism for producing concentrated urine cannot include the obligatory reabsorption of water in the proximal convoluted tubule since this process is part of the nephron, the system that filters the blood. Glucose and amino acids are reabsorbed almost entirely, as are approximately 70% of filtered potassium and 80% of bicarbonate.

Have a nice day!

4 0
3 years ago
Archer is a soil scientist and needs to examine a bacteria sample. He wants to be able to change his magnification with differen
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Answer:

C. Dissecting microscope

Explanation:

It is trying to see the surface

3 0
3 years ago
What is commonly used to run a central heating system?
Troyanec [42]
Answer :- Electrical energy

Explanation :-
Geothermal energy is too large scale
solar energy is inefficient
Nuclear does more harm
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3 years ago
What does the difference in potential energy between the reactants and products represent? A. It represents the energy required
Scrat [10]

Answer:

B. It represents the change in enthalpy for the reaction.

Explanation:

The potential energy diagram for a chemical reaction shows its potential energy plotted against the reaction progress coordinate. The potential energy diagram shows how the potential energy of reactants and products vary as reactants are converted into products.

The potential energy of the system refers to energy stored in the chemical bonds of reactants and products. The difference between the potential energy of reactants and products is known as the enthalpy of reaction. This difference in potential energy may be positive or negative. A positive difference in potential energy implies an endothermic reaction while a negative difference in potential energy implies an exothermic reaction.

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