a) When the reaction takes place a yellow precipitate will be formed.
b) The law of conservation of mass is true.
<u>Explanation:</u>
a) When a lead nitrate solution is mixed with a potassium chromate solution, a yellow precipitate containing lead forms according to the equation:
→ 
b) Law of conservation of mass for the given reaction is true.
From the given table we know the mass of reactants and its products.
Law of conservation of mass is a principle when a reaction takes place in a closed system, the mass of the products and reactants in the system doesn't change.
⇒The sum of the mass of the reactants = The sum of the mass of the products.
The sum of the reactants = 128.71+128.97.
= 257.68 g.
The sum of the products = 154.10+103.58.
= 257.68 g.
Thus law of conservation of mass is true for the above reaction.
Explanation:
Each element in the periodic table has different but fixed number of the protons in nucleus of it's atom, which is known as the atomic number.
Transmutation of one chemical element into the another involves the changing of the atomic number. Such nuclear reaction requires millions of the times more energy as compared to normal chemical reactions. Thus, the dream of the alchemist of transmuting the lead into the gold was never achievable chemically .
Conversion of lead to gold in today's world:
This conversion is indeed possible. The requirements are a particle accelerator, tremendous supply of the energy. Nuclear scientists at the Lawrence Berkeley National Laboratory located in California, more than 30 years ago, succeeded in producing very minute amounts of the gold from the bismuth. Bismuth is a metallic element which is adjacent to the lead on periodic table. Same process would work for the lead but isolating gold at end of reaction would prove much more difficult because lead is available in many isotopes. The homogeneous nature of the element means that it is easier to separate the gold from the bismuth as compared to separate the gold from the lead which has four isotopic identities which all are stable.
140 g of nitrogen (N₂)
Explanation:
We have the following chemical equation:
N₂ + 3 H₂ -- > 2 NH₃
Now, to find the number of moles of ammonia we use the Avogadro's number:
if 1 mole of ammonia contains 6.022 × 10²³ molecules
then X moles of ammonia contains 6.022 × 10²⁴ molecules
X = (1 × 6.022 × 10²⁴) / 6.022 × 10²³
X = 10 moles of ammonia
Taking in account the chemical reaction we devise the following reasoning:
If 1 mole of nitrogen produces 2 moles of ammonia
then Y moles of nitrogen produces 10 moles of ammonia
Y = (1 × 10) / 2
Y = 5 moles of nitrogen
number of moles = mass / molecular weight
mass = number of moles × molecular weight
mass of nitrogen (N₂) = 5 × 28 = 140 g
Learn more about:
Avogadro's number
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