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3 years ago

Help please will give brainly if right

Chemistry

1 answer:

jeka57 [31]3 years ago

4 0

Answer:

B and D

Explanation:

Because its adaptions they need to survive in the cold.

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Plllllllllllllllllllllllllllllllll hellllllllllllllllppppppppppppppp mmmmmmmmmmmeeeeeeee

kykrilka [37]

Answer:b yes b yes c no c yes d yes d no

Explanation: wanna trade r o b l o x acc

7 0

3 years ago

Element X is a radioactive isotope such that every 82 years, its mass decreases by half. Given that the initial mass of a sample

lesantik [10]

Answer: 17 years

Explanation:

Expression for rate law for first order kinetics for radioactive substance is given by:

$t=\frac{2.303}{k}\log\frac{a}{a-x}$

where,

k = rate constant

t = age of sample

a = let initial amount of the reactant

a - x = amount left after decay process

a) for completion of half life:

Half life is the amount of time taken by a radioactive material to decay to half of its original value.

$t_{\frac{1}{2}}=\frac{0.693}{k}$

$k=\frac{0.693}{82years}=8.4\times 10^{-3}years^{-1}$

b) for 8900 g of the mass of the sample to reach 7700 grams

$t=\frac{2.303}{8.4\times 10^{-3}}\log\frac{8900}{7700}$

$t=17years$

Thus it will take 17 years

4 0

3 years ago

What is the % yield when 140.0 grams of Ethylene gas (C2H4) reacts with excess chlorine to form 280.0 grams of 1,2-Dichloro Etha

KatRina [158]

Answer:

percent yield = 56.6 %

Explanation:

Data given:

mass of Ethylene gas (C₂H₄) = 140 g

actual yield of 1,2-Dichloro Ethane (C₂H₄Cl₂)= 280 g

percent yield of 1,2-Dichloro Ethane (C₂H₄Cl₂) = ?

Reaction Given:

C₂H₄ + Cl₂ -------> C₂H₄Cl₂

Solution:

First we have to find theoretical yield.

So,

Look at the reaction

C₂H₄ + Cl₂ -----—> C₂H₄Cl₂

1 mol 1 mol

As 1 mole of C give 1 mole of CH₄

Convert moles to mass

molar mass of C₂H₄ = 2(12) + 4(1)

molar mass of C₂H₄ = 24 + 4

molar mass of C₂H₄ = 28 g/mol

molar mass of C₂H₄Cl₂ = 2(12) + 4(1) + 2(35.5)

molar mass of C₂H₄Cl₂ = 24 + 4 + 71

molar mass of C₂H₄Cl₂ = 99 g/mol

Now

C₂H₄ + Cl₂ -----—> C₂H₄Cl₂

1 mol (28 g/mol) 1 mol (99 g/mol)

28 g 99 g

28 grams of Ethylene gas (C₂H₄) produce 99 grams of C₂H₄Cl₂

if 28 g of C₂H₄ produce 99 g of C₂H₄Cl₂ so how many grams of C₂H₄Cl₂ will be produced by 140 g of C₂H₄.

Apply Unity Formula

28 g of C₂H₄ ≅ 99 g of C₂H₄Cl₂

140 g of C₂H₄≅ X of C₂H₄Cl₂

Do cross multiply

mass of C₂H₄Cl₂ = 99 g x 140 g / 28 g

mass of C₂H₄Cl₂ = 495 g

So the Theoretical yield of 1,2-Dichloro Ethane (C₂H₄Cl₂)= 495 g

Now Find the percent yield of 1,2-Dichloro Ethane (C₂H₄Cl₂)

Formula Used

percent yield = actual yield /theoretical yield x 100 %

Put value in the above formula

percent yield = 280g / 495 g x 100 %

percent yield = 56.6 %

percent yield of 1,2-Dichloro Ethane (C₂H₄Cl₂) = 56.6 %

8 0

4 years ago

An atom has 5 protons and 7 neutrons

attashe74 [19]

Answer:

i dont understand what u are trying to say

Explanation:

8 0

3 years ago

How many copper atoms are in 150 g of copper metal

GaryK [48]

1. From grams -> mole:

=grams given x 1 mol/molar mass

So 150 g Cu x 1 mol Cu/63.546 g Cu = 2.4 mol Cu

2. From mole -> atoms

=number of mol x 6.022x10^22 atoms/1 mol

So 2.4 mol Cu x 6.022x10^22 atoms Cu/1 mol Cu = 1.4 x 10^24 atoms Cu

5 0

3 years ago