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3 years ago

List four rules for rounding numbers.

Chemistry

1 answer:

sveta [45]3 years ago

3 0

Answer:

the number you are rounding is followed by 5, 6, 7, 8, or 9, round the number up. Example: 38 rounded to the nearest ten is 40

If the number you are rounding is followed by 0, 1, 2, 3, or 4, round the number down. Example: 33 rounded to the nearest ten is 30

Rounding fractions works exactly the same way as rounding whole numbers. The only difference is that instead of rounding to tens, hundreds, thousands, and so on, you round to tenths, hundredths, thousandths, and so on.

By rounding off, you could easily figure out that you would need about $6.00 to pay for your groceries.

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Calculate the enthalpy of reaction for 2CO + O2 → 2CO2. given the following bond energies:

kotegsom [21]

Answer : The enthalpy change for the reaction is 1043 kJ/mol.

Explanation :

The given chemical reaction is:

$2CO+O_2\rightarrow 2CO_2$

As we know that:

The enthalpy change of reaction = E(bonds broken) - E(bonds formed)

$\Delta H=[(2\times B.E_{C\equiv O})+(1\times B.E_{O\equiv O})]-[2\times B.E_{C=O}]$

Given:

$B.E_{C\equiv O}$ = 1074 kJ/mol

$B.E_{O\equiv O}$ = 499 kJ/mol

$B.E_{C=O}$ = 802 kJ/mol

Now put all the given values in the above expression, we get:

$\Delta H=[(2\times 1074kJ/mol)+(1\times 499kJ/mol)]-[2\times 802kJ/mol]$

$\Delta H=1043kJ/mol$

Therefore, the enthalpy change for the reaction is 1043 kJ/mol.

7 0

3 years ago

31 Which ion has the smallest radius? (1) O2-(2) S2-(3) Se2- (4) Te2-

bearhunter [10]

The answer 1) Oxygen. And another smallest radius is fluorine, because it is the first in the periodic table.

6 0

3 years ago

What is the mass in milligrams of 4.30 moles of sodium?use âeâ for âÃ10" and use significant figures?

Elis [28]

First, calculate the mass of sodium in g with the help of molar mass and number of moles.

Number of moles = $\frac{given mass in g}{molar mass}$ (1)

Molar mass of sodium = $23 .0 g/mol$

Substitute the given value of number of moles and molar mass of sodium in formula (1)

$4.30 moles = \frac{given mass in g}{23.0 g/mol}$ (1)

$4.30 moles\times 23.0 g/mol = mass in g$ (1)

mass of sodium in g = $98.9 g$

Now, according to conversion factor, 1 g = 1000 mg

So, $98.9 g$ of sodium = $98.9 \times 1000 mg$

= $98900 mg$ of sodium

Thus, mass of sodium in mg = $9.89 \times 10^{4} mg$

8 0

3 years ago

Determine whether each molecule is polar or nonpolar.

JulsSmile [24]

A) Sulfur dichloride (SCl₂) is polar molecule because is bent with asymmetric charge distribution around the central atom (S).
b) Sulfur tetrachloride (SCl₄) is polar because there is lone electron pair around the sulfur.
c) Bromine pentachloride (BrCl₅) is polar because dipole moment do not cancel.

6 0

3 years ago

How many moles in 44.7 kg of carbon dioxide

slava [35]

Answer:

What is the number of moles of carbon present in 44 grams of carbon dioxide? One. 44 grams is a mole of carbon dioxide and there is one carbon atom in CO 2 so there is one mole of carbon. That’s how chemistry works.

Explanation:

7 0

2 years ago