What is the only sure evidence for a chemical reaction?

A sample of aluminum, which has a specific heat capacity of , is put into a calorimeter (see sketch at right) that contains of w

Oksanka [162]

Complete Question

A sample of aluminum, which has a specific heat capacity of 0.897 JB loc ! is put into a calorimeter (see sketch at right) that contains 200.0 g of water. The aluminum sample starts off at 85.6 °C and the temperature of the water starts off at 16.0 °C. When the temperature of the water stops changing it's 20.1 °C. The pressure remains constant at 1 atm. Calculate the mass of the aluminum sample.

Answer:

$M=58g$

Explanation:

From the question we are told that:

Heat Capacity $H=0.897$

Mass of water $M=200g$

Initial Temperature of Aluminium $T_a=85.6$

Initial Temperature of Water $T_{w1}=16.0$

Final Temperature of Water $T_{w2}=16.0$

Generally

Heat loss=Heat Gain

Therefore

$M*0.897*(85.6-20.1) =200*4.184*(20.1-16)$

$M=58g$

5 0

2 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]

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

Explanation:

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

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

For nickel:

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:

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

For nickel (II) oxide:

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:

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

For aluminium:

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

2 years ago

What is the molality of a solution that is obtained by dissolving 2.922 g of NaCl into 1000.0 g of water if the molar mass of Na

never [62]

In order to find molarity, you must first find the number of moles that was dissolved.

Now, Moles = Mass ÷ Molar Mass

⇒ Moles of NaCl = 2.922 g ÷ 58.44 g/mol

= 0.05 moles

∴ the Molarity of the NaCl is 0.05 M [Option 1]

4 0

2 years ago

A chemist sets up a chemical reaction but finds that none of the reactant molecules have a required activation energy. What is t

Anvisha [2.4K]

Activation energy is the minimum amount of energy that the colliding reactant molecules must possess for the formation of products. Lower the activation energy, higher will be chance of formation of products. So activation energy is the minimum energy requirement that has to overcome for the reaction to be completed. Therefore, when in a chemical reaction the reactant molecules do not collide with required activation energy, the collisions will not be fruitful even if they are properly oriented which means that the products will not form.

Hence the correct answer will be B.) no products will be formed

5 0

2 years ago

Read 2 more answers

What was removed from the glucose molecules when they bonded to form maltose

steposvetlana [31]

Answer:

Two hydrogen atoms and one oxygen atom (water) was removed.

Explanation:

yw:))

5 0

3 years ago