Answer:
100ml of a stock 50% KNO3 solutions are needed to prepare 250ml of a 20% KNO3 solution.
Explanation:
In the given question it is mentioned that
S1=50%
V2=250ml
S2= 20%
We all know that
V1S1=V2S2
∴V1= V2×S2÷S1
∴V1= V2S2×1/S1
∴V1= 250×20÷50
∴V1= 100ml
Answer:
A compound
Example:
Sugar contains carbon, hydrogen and oxygen. Water (H2O) has two hydrogen atoms (H2) and one oxygen atom (O). So both sugar and water are chemical compounds. Together they are a mix of chemical compounds.
Answer : The enthalpy of the reaction is, -2552 kJ/mole
Explanation :
According to Hess’s law of constant heat summation, the heat absorbed or evolved in a given chemical equation is the same whether the process occurs in one step or several steps.
According to this law, the chemical equation can be treated as ordinary algebraic expression and can be added or subtracted to yield the required equation. That means the enthalpy change of the overall reaction is the sum of the enthalpy changes of the intermediate reactions.
The given enthalpy of reaction is,

The intermediate balanced chemical reactions are:
(1)

(2)

(3)

(4)

Now we have to revere the reactions 1 and multiple by 2, revere the reactions 3, 4 and multiple by 2 and multiply the reaction 2 by 2 and then adding all the equations, we get :
(when we are reversing the reaction then the sign of the enthalpy change will be change.)
The expression for enthalpy of the reaction will be,



Therefore, the enthalpy of the reaction is, -2552 kJ/mole
Answer:
F = 30 N
Explanation:
Given data:
Mass of toy train = 1.5 kg
Acceleration of train = 20 m/s²
Amount of force acting on it = ?
Solution:
The net force on object is equal to the its mass multiply by its acceleration.
Formula:
F = ma
F = force
m = mass
a = acceleration
Now we will put the values in formula.
F = 1.5 kg × 20ms⁻²
F = 30 kg.ms⁻²
kg.ms⁻² = N
F = 30 N
Answer:
Elements and compounds are two types of pure substances.
Explanation: