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Answer:
J (joule) W(watt)
Explanation:
If you're looking for the definition it is
The most common definition of energy is the work that a certain force can do. Energy also cannot be created or destroyed and some examples are
light, heat, mechanical, potential, and kinetic
The mass of the piece of wood is 35.58 g.
Joule = M × T × C
Where, M = mass
T = change in temperature(42C-23C=19 C)
C = specific heat capacity = 1.716 joules/gram
Substituting the values in the equation,
1160 = M × 19 × 1.716
M = 1160/32.604 = 35.58 g
Therefore, the mass of the piece of wood = 35.58 g
<h3>What is meant by specific heat capacity?</h3>
A material's specific heat capacity, which is defined as its heat capacity divided by its mass, determines how much energy is required to increase a gram's temperature by one degree Celsius (or one Kelvin)
<h3>What is mass?</h3>
Mass is the quantity of matter in a physical body.
To learn more about specific heat capacity visit:
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Answer:
The empirical formula of a compound is Na2Cr2O7
Explanation:
Empirical formula is defined as the lowest ratio of elements present in any substance. In order to determine the empirical formula for a substance containing these elements we have to follow some steps.
1.In the first step, we have to divide the given mass of an element with its molecular mass to convert the mass to moles.

Similarly, the moles of Cr and O in that compound were calculated and found as 0.396 and 1.3875, respectively.
2. Then the next step is to determine the lowest moles and divide all the moles with that lowest mole. As here the lowest mole is 0.396. So on dividing the moles of Na, Cr and O with 0.396, we will obtain the ratio as 1:1:3.5.
3. As the ratio consists of a fractional number, we have to multiply it with the smallest possible integer to convert it to whole number. In this case, if we multiply it with 2 , we will get the ratio as 2:2:7.
Thus, the empirical formula for the compound can be written as Na2Cr2O7.
Solid Magnesium is considered as active metal so it reacts with strong acids like HCl and H₂SO₄ liberating Hydrogen gas according to the following equations:
Mg(s) + 2 HCl(aq) → MgCl₂(aq) + H₂(g)
Mg(s) + H₂SO₄(aq) → MgSO₄(aq) + H₂(g)
so the amount of solid magnesium decrease by addition of strong acid to it.