Answer:
d) The dilution equation works because the number of moles remains the same.
Explanation:
Let’s say that you have 1 mol of a solute in I L of solution. The concentration is 1 mol·L⁻¹. and <em>M</em>₁<em>V</em>₁ = 1 mol.
Now, you dilute the solution to a volume of 2 L. You still have 1 mol of solute, but in 2 L of solution. The new concentration is 0.5 mol·L⁻¹.
The volume has doubled, but the volume has halved, and <em>M</em>₂<em>V</em>₂ = 1 mol.
b) <em>Wrong</em>. The molar concentration changes on dilution.
c) <em>Wrong</em>. The volume changes on dilution.
a) <em>Wrong</em>, although technically correct, because if the moles don’t change, the mass doesn’t change either. However, the formula <em>M</em>₁<em>V</em>₁ has units mol·L⁻¹ × L = mol. Thus, in the formula, it is moles that are constant.
Half life is the time taken for a radioactive isotope to decay by half its original mass. In this case the half life of carbon-14 is 5.730 years.
Using the formula;
New mass = original mass × (1/2)^n; where n is the number of half lives (in this case n=1 )
New mass = 2 g × (1/2)^1
= 1 g
Therefore; the mass of carbon-14 that remains will be 1 g
Answer:
4.5 kilograms of silicon dioxide is required to produce 3.00 kg of SiC.
Explanation:
The balanced equation for the reaction between silicon dioxide and carbon at high temperature is given as:
1 mole silicon dioxide reacts with 3 moles of carbon to give 1 moles of silicon carbide and 2 moles of carbon monoxide.
Mass of SiC = 3.00kg = 3000.00 g
1 kg = 1000 g
Molecular mass of SiC = 40 g/mol
Moles of SiC = 
According to reaction, 1 mole of SiC is produced from 1 mole of silicon dioxide.
Then 75 moles of SiC will be produce from:
of silicon dioxide.
mass of 75 moles of silicon dioxde:
4.5 kilograms of silicon dioxide is required to produce 3.00 kg of SiC.
