In order to determine the density of an item, we will need to determine its mass and volume. The standard unit for measuring mass in a lab is the gram. Think about liquids- what units do you typically report the volume of a liquid in? What about for a sugar cube, what volume is the most appropriate?
A regular object like a sugar cube can be measured with a ruler so we might report the volume in centimeters cubed (cm3). An irregular object like the plate pictured below can be measured by using a technique called volume by displacement. A liquid (typically water) is placed in a graduated cylinder and the volume of a liquid is measured. Then the irregular object is placed in the liquid and the volume is measured again. The change in volume is the irregular object’s volume. This measurement is often made using a graduated cylinder and recording a volume in Liters or milliliters (mL).
Figure 1. (a) Regular object of metal blocks with the same width, length, and height. (B) An irregular
We may apply a mass balance here. The total moles of NaCl will remain constant before and after the mixing of the solutions. We have three solutions:
1) 25 ml of 5 M NaCl
2) 100 ml of 0 M NaCl
3) A mixture of these solutions with volume 125 ml and concentration C
The moles of a substance are equal to the product of the concentration and volume. Thus:
25 * 5 + 100 * 0 = 125 * C
C = 1 M
The concentration of the final solution is 1 M.
2H2O --> 2H2 + O2
The mole H2O:mole O2 ratio is 2:1
Now determine how many moles of O2 are in 50g: 50g × 1mol/32g = 1.56 moles O2
Since 1 mole of O2 was produced for every 2 moles of H2O, we need 2×O2moles = H2O moles
2×1.56 = 3.13 moles H2O
Finally, convert moles to grams for H2O:
3.13moles × 18g/mol = 56.28 g H2O
D) 56.28
Answer:
D. It is a chemical reaction because the total mass remains the same when new substances are formed.
Explanation:
A chemical reaction is represented by a chemical equation which show the reactant and products. Reactants are written on left side of arrow while products are written on right side. The number of atoms are remain same however arrangement of atoms is different on both side.
For example:
6H₂O + 6CO₂ + energy → C₆H₁₂O₆ + 6O₂
it is known from balanced chemical equation that 6 moles of carbon dioxide react with the six moles of water and created one mole of glucose and six mole of oxygen. The number of atoms are same on both side however arrangement of atoms is different.
While in case of nuclear reaction small change in mass take place.
The concentration of mixed solution = 0.5 M
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Further explanation
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Given
0.5 M HCl
0.5 M Ca(OH)₂
Required
The concentration
Solution
Molarity from 2 solutions :
Vm Mm = V₁. M₁ + V₂. M₂
m = mixed solution
V = volume
M = molarity
V = mixed volume
1 = solution 1
2 = solution 2
Vm = V₁+V₂
Equal volumes⇒V₁=V₂, and Vm = 2V, then equation becomes :
2V.Mm = V(M₁+M₂)
2V.Mm = V(0.5+0.5)
Mm=0.5 M
