Question #1
Potasium hydroxide (known)
volume used is 25 ml
Molarity (concentration) = 0.150 M
Moles of KOH used
0.150 × 25/1000 = 0.00375 moles
Sulfuric acid (H2SO4)
volume used = 15.0 ml
unknown concentration
The equation for the reaction is
2KOH (aq)+ H2SO4(aq) = K2SO4(aq) + 2H2O(l)
Thus, the Mole ratio of KOH to H2SO4 is 2:1
Therefore, moles of H2SO4 used will be;
0.00375 × 1/2 = 0.001875 moles
Acid (sulfuric acid) concentration
0.001875 moles × 1000/15
= 0.125 M
Question #2
Hydrogen bromide (acid)
Volume used = 30 ml
Concentration is 0.250 M
Moles of HBr used;
0.25 × 30/1000
= 0.0075 moles
Sodium Hydroxide (base)
Volume used 20 ml
Concentration (unknown)
The equation for the reaction is
NaOH + HBr = NaBr + H2O
The mole ratio of NaOH : HBr is 1 : 1
Therefore, moles of NaOH used;
= 0.0075 moles
NaOH concentration will be
= 0.0075 moles × 1000/20
= 0.375 M
Answer:
There are five signs of a chemical change:
Colour Change.
Production of an odour.
Change of Temperature.
Evolution of a gas (formation of bubbles)
Precipitate (formation of a solid).
Answer:
During photosynthesis SOLAR enerrgy is transformed into CHEMICAL energy.
Explanation:
In nutrition, green plants manufactures their own food which they use for both energy and growth. This is called an autotrophic mode of nutrition.
Therefore, photosynthesis is an autotrophic nutrition in which plant can build sugar by taking carbon dioxide from air and water from the soil. For the synthesis of sugar like glucose, carbon dioxide provides carbon
and oxygen whereas water molecules provide hydrogen. The plant builds sugar molecules from these simple compounds. Enzymes needed for this purpose are present in the cells and energy is trapped by chlorophyll from sunlight. This process is summarised in the equation below:
Sunlight (solar)
6CO2 + 6H2O--------------------> C6H12O6 + 6O2
From the equation, Carbon dioxide, water and sunlight (SOLAR energy) is the raw materials needed to produce Glucose and oxygen (CHEMICAL energy) as by products.
The answer is:
1. 500g stainless steel cup
<span>2. 500g aluminum cup </span>
<span>3. 750g aluminum cup</span>
The sum of angels of a quadrilateral is equal to 360°.
∠A = 360 - (60 + 45 + 100) = 155
