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shtirl [24]
4 years ago
8

78.9 + 890.43 - 21 = 9.5 x 10^2

Chemistry
1 answer:
maria [59]4 years ago
8 0

948 or 9.48 x 10^2

There are two sets of rules for significant figures

• One set for addition and subtraction

• Another set for multiplication and division

You used the set for multiplication and division.

This problem involves addition and subtraction, and the rule is

The number of places after the decimal point in the answer must be <em>no greater than the number of decimal places in every term</em> in the sum.

Thus, we have

78.9

+890.43

-21.

= 948.33

The "21" term has the fewest digits after the decimal point (none), so the answer must have no digits after the decimal point.

To the correct answer is 948 = 9.48 x 10^2. It has three significant figures.

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Whats the answer and how you got it please :-)
marta [7]
For the element chlorine to be "happy", it needs 8 valence electrons meaning it needs 8 electrons on its outer shell. So the answer would be chlorine because it has 7 valence electrons in the picture and it needs one more to be considered stable.
4 0
4 years ago
How many total of atoms are in 0.370gr of P2O5
Irina-Kira [14]
142 g ---------------- 6.02 x 10²³ molecules
0.920g g ------------ ( molecules )

molecules = 0.920 x ( 6.02 x 10²³ ) / 142

molecules = 5.53 x 10²³ / 142

= 3.89 x 10²¹ molecules

1 molecule P2O5 -------------------------- 7 atoms
3.89 x 10²¹ molecules -------------------- ( atoms )

atoms = ( 3.89 x 10²¹) x 7 / 1

atoms = <span>2.72 x 10²² atoms of P2O5


 Hope this helps!!!
</span>
8 0
3 years ago
How much MgO is made when 12Kg of Mg is completely burned in air?
Flauer [41]

Answer:

Mass = 20,000 g  

Explanation:

Given data:

Mass of MgO formed = ?

Mass of Mg react = 12 Kg (12 Kg × 1000/1 Kg = 12000 g)

Solution:

Chemical equation:

2Mg + O₂     →   2MgO

Number of moles of Mg:

Number of moles = mass/molar mass

Number of moles = 12000 g/ 24 g/mol

Number of moles = 500 mol

Now we will compare the moles of Mg and MgO.

             Mg          :           MgO

             2             :           2

            500         :          500

Mass of MgO:

Mass = number of moles × molar mass

Mass = 500 mol × 40 g/mol

Mass = 20,000 g  

8 0
3 years ago
A 0.500 g sample of tin (Sn) is reacted with oxygen to give 0.534 g of product. What is the percent mass of the tin and percent
AleksAgata [21]

Answer:

Percentage mass of Tin = 96.3%

Percentage mass of oxygen = 6.40%

Explanation:

The product of the reaction is an oxide of tin.

Assuming all of the 0.500 g sample of tin reacted with oxygen to produce the oxide:

Mass of oxide = 0.534 g

Mass of tin present in the oxide = 0.500 g

Mass of oxygen in the oxide = 0.534 g of oxide - 0.500 g Sn = 0.034 g O

Percentage composition = mass of element/mass of compound × 100%

Percentage composition of Sn = 0.500 g/0.534 g × 100 = 93.6% Sn

Percentage composition of oxygen = 0.034 g/0.534 g × 100 = 6.40%

6 0
4 years ago
What volume of air contains 10.0g of oxygen gas at 273 k and 1.00 atm?
VARVARA [1.3K]
12.3g 02times1 mol 02/32.0 g 02=mol 02
.38mol/x=20.95/100
x=1.8mol air... 

PV=nRT

101.3kPa times V =1.8 mol times 8.31[kPa *L]/{k*mol}*273k
V=40.3Lair
7 0
3 years ago
Read 2 more answers
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