Answer: Ice is melting due to the transfer of thermal energy from Jan's hand to ice.
Explanation: The melting of ice is a physical change and is happening when the thermal energy from Jan's hand is transferred to ice. Due to this energy transfer, the particles of ice starts to move faster and hence, making the ice melt.
In this, the physical state of ice is changing from solid to liquid state.

<h3><u>Answer;</u></h3>
Exothermic chemical reaction
<h3><u>Explanation;</u></h3>
- Exothermic reactions are chemical reactions where the products have less energy that the reactants.
- Exothermic reactions give off energy, usually in the form of heat, while endothermic reactions absorb energy.
- The combustion of propane is definitely an exothermic reaction because it generates a lot of heat.
The correct answer is B. H2SO4 + B(OH)3 B2(SO4)3 + H2O
Hope this helps!
Answer:- 0.138 M
Solution:- The buffer pH is calculated using Handerson equation:

acts as a weak acid and
as a base which is pretty conjugate base of the weak acid we have.
The acid hase two protons(hydrogen) where as the base has only one proton. So, we could write the equation as:

Phosphoric acid gives protons in three steps. So, the above equation is the second step as the acid has only two protons and the base has one proton.
So, we will use the second pKa value. The acid concentration is given as 0.10 M and we are asked to calculate the concentration of the base to make a buffer of exactly pH 7.00.
Let's plug in the values in the equation:



Taking antilog:


On cross multiply:
[base] = 1.38(0.10)
[base] = 0.138
So, the concentration of the base that is
required to make the buffer is 0.138M.
Answer:
Explanation:
So basically it just asking you question about that surtain subject .