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3 years ago

5

In which sample of water do the water particles have more energy: 5 grams of ice cubes at -10 degrees Celsius or 5 grams of liqu

id water at 20 degrees Celsius? How do you know

1 answer:

Ivenika [448]3 years ago

6 0

Higher temperature = higher energy. In water it is a liquid as the particles have more energy so vibrate and are further away from each other.

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Carbon-14 has a half-life of approximately 5700 years. How much of a 1000g sample will be left undecayed and still radioactive a

Artist 52 [7]

Answer:

option C is correct (250 g)

Explanation:

Given data:

Half life of carbon-14 = 5700 years

Total amount of sample = 1000 g

Sample left after 11,400 years = ?

Solution:

First of all we will calculate the number of half lives passes during 11,400 years.

Number of half lives = time elapsed/ half life

Number of half lives = 11,400 years/5700 years

Number of half lives = 2

Now we will calculate the amount left.

At time zero = 1000 g

At first half life = 1000 g/2 = 500 g

At second half life = 500 g/2 = 250 g

Thus, option C is correct.

4 0

3 years ago

If the molar mass of the compound in problem 3 is 73.8 grams/mole? what is the molecular formula ?

umka21 [38]

The molecular formula would be Li2CO3

7 0

2 years ago

hichkok12 [17]

Answer: B

Explanation: I answered randomly

5 0

3 years ago

Over the years, the thermite reaction has been used for welding railroad rails, in incendiary bombs, and to ignite solid-fuel ro

melamori03 [73]

<u>Answer:</u> The mass of nickel (II) oxide and aluminium that must be used is 18.8 g and 4.54 g respectively.

<u>Explanation:</u>

To calculate the number of moles, we use the equation:

$\text{Number of moles}=\frac{\text{Given mass}}{\text{Molar mass}}$ .....(1)

<u>For nickel:</u>

Given mass of nickel = 14.8 g

Molar mass of nickel = 58.7 g/mol

Putting values in equation 1, we get:

$\text{Moles of nickel}=\frac{14.8g}{58.7g/mol}=0.252mol$

For the given chemical reaction:

$3NiO(s)+2Al(s)\rightarrow 3Ni(l)+Al_2O_3(s)$

<u>For nickel (II) oxide:</u>

By Stoichiometry of the reaction:

3 moles of nickel are produced from 3 moles of nickel (II) oxide

So, 0.252 moles of nickel will be produced from $\frac{3}{3}\times 0.252=0.252mol$ of nickel (II) oxide

Now, calculating the mass of nickel (II) oxide by using equation 1:

Molar mass of nickel (II) oxide = 74.7 g/mol

Moles of nickel (II) oxide = 0.252 moles

Putting values in equation 1, we get:

$0.252mol=\frac{\text{Mass of nickel (II) oxide}}{74.7g/mol}\\\\\text{Mass of nickel (II) oxide}=(0.252mol\times 74.7g/mol)=18.8g$

<u>For aluminium:</u>

By Stoichiometry of the reaction:

3 moles of nickel are produced from 2 moles of aluminium

So, 0.252 moles of nickel will be produced from $\frac{2}{3}\times 0.252=0.168mol$ of aluminium

Now, calculating the mass of aluminium by using equation 1:

Molar mass of aluminium = 27 g/mol

Moles of aluminium = 0.168 moles

Putting values in equation 1, we get:

$0.168mol=\frac{\text{Mass of aluminium}}{27g/mol}\\\\\text{Mass of aluminium}=(0.168mol\times 27g/mol)=4.54g$

Hence, the mass of nickel (II) oxide and aluminium that must be used is 18.8 g and 4.54 g respectively.

4 0

3 years ago

2 H2 + O2= 2 H2O

AVprozaik [17]

Answer:

the answer is 4.0moles

Explanation:

1mole of O2 produce 2moles of H2O/x mole will produce 8.0moles of H2O then the answer is 4.0moles.

3 0

3 years ago