Hello! Specific heat is the amount of energy required by known amount of substance to raise its temperature by one degree celsius. In our question it is given that 2000J energy when supplied to 125 g of unknown substance raised its temperature by 18 oC. So, The specific heat is calculated as follow;
Answer:
Mass = 36 g
Explanation:
Given data:
Mass of water formed = ?
Mass of hydrogen = 4.04 g
Mass of oxygen = 31.98 g
Solution:
Chemical equation:
2H₂ + O₂ → 2H₂O
Number of moles of hydrogen:
Number of moles = mass/molar mass
Number of moles = 4.04 g/ 2 g/mol
Number of moles = 2.02 mol
Number of moles of oxygen:
Number of moles = mass/molar mass
Number of moles = 31.98 g/ 32 g/mol
Number of moles = 1.0 mol
Now we will compare the moles of water with hydrogen and oxygen.
O₂ : H₂O
1 : 2
H₂ : H₂O
2 : 2
2.02 : 2.02
Number of moles of water formed by oxygen are less thus oxygen will limiting reactant.
Mass of water:
Mass = number of moles × molar mass
Mass = 2 mol × 18 g/mol
Mass = 36 g
Answer:
The percent by mass of water in this crystal is:
Explanation:
This exercise can be easily solved using a simple rule of three where the initial weight of the hydrated crystal (6,235 g) is taken into account as 100% of the mass, and the percentage to which the mass of 4.90 g corresponds (after getting warm). First, the values and unknown variable are established:
- 6,235 g = 100%
- 4.90 g = X
And the value of the variable X is found:
- X = (4.90 g * 100%) / 6,235 g
- X = approximately 78.6%.
The calculated value is not yet the percentage of the water, since the water after heating the glass has evaporated, therefore, the remaining percentage must be taken, which can be calculated by subtraction:
- Water percentage = Total percentage - Percentage after heating.
- <u>Water percentage = 100% - 78.6% = 21.4%</u>
