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CaHeK987 [17]
2 years ago
10

Which of the following is always a reactant in a combustion reaction? (5 points)

Chemistry
1 answer:
aleksandr82 [10.1K]2 years ago
4 0

Answer:

A

Explanation:

Combustion reaction always has something hydrocarbon plus oxygen gas which equals to carbon dioxide and water. Always being a reactant in a combustion reaction is oxygen, since reactants are what we start off the reaction with.

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How much energy in joules is released when 18.5 grams of copper cools from 285 °C<br> down to 45 °C
nadya68 [22]

Answer: 1709.4 Joules

Explanation:

The quantity of Heat Energy (Q) released on cooling a heated substance depends on its Mass (M), specific heat capacity (C) and change in temperature (Φ)

Thus, Q = MCΦ

Since Q = ?

M = 18.5 grams

Recall that the specific heat capacity of copper C = 0.385 J/g.C

Φ = 285°C - 45°C = 240°C

Then, Q = MCΦ

Q = 18.5grams x 0.385 J/g.C x 240°C

Q = 1709.4 Joules

Thus, 1709.4 Joules is released when copper is cooled.

5 0
3 years ago
Indicate the number of significant figures in the following measured numbers:
inysia [295]

Answer: a = 2 ; f = 5 ; b = 2 ; g = 2 ; c = 2 ; h = 2 ; d = 4 ; i = 5 ; e = 3 ; j = 7

Explanation: Some rules to follow while calculating sig figs is

1. If a number like 4500 is present, only two sig figs are counted, but none of the zeros are, but if 4500. has a decimal point present, then you should count all the numbers available.

2. If a number like .0005 is present, only count 5 as a sig fig, however if the number is .00050, count the 0 after the 5 in this example (this would then have two sig figs.

3 0
2 years ago
A compound with a molar mass of 60g/mol is 40.4% carbon, 6.7% hydrogen and 53.3% oxygen (by mass). determine the emperical and m
Fittoniya [83]

<span>A compound is found to be 40.0% carbon, 6.7% hydrogen and 53.5% oxygen. Its molecular mass is 60. g/mol. 
</span>Q1)
Empirical formula is the simplest ratio of whole numbers of components making up a compound.
the percentages have been given, therefore we can calculate for 100 g of the compound.

                                C                            H                        O
Mass in 100 g      40.0 g                       6.7 g                   53.5 g
Molar mass            12 g/mol                1 g/mol                 16 g/mol
Number of moles   40.0/12= 3.33         6.7/1 = 6.7          53.5/16 = 3.34
Divide by the least number of moles  
                             3.33/3.33 = 1           6.7/3.33 = 2.01   3.34/3.33 = 1.00
after rounding off
C - 1 
H - 2
O - 1

Empirical formula - CH₂O

Q2)
Molecular formula is the actual number of components making up the compound.
To find the number of empirical units we have to find the mass of one empirical unit.
Mass of one empirical unit = CH₂O - 12 + (1x2) + 16 = 30 g
Mass of one mole of compound = 60 g
Number of empirical units = 60 g / 30 g = 2
Therefore molecular formula - 2(CH₂O) 
 Molecular formula - C₂H₄O₂
4 0
3 years ago
During the process of sublimation,
Len [333]
During this process. A. Solid turns directly into a Gas.
5 0
3 years ago
PLEASE ANSWER FAST
worty [1.4K]
C is the answer.
The temperature T<span> in degrees Celsius (°C) is equal to the temperature </span>T<span> in Kelvin (K) minus 273</span>°.
6 0
3 years ago
Read 2 more answers
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